Linux 5.1.15

[linux/fpc-iii.git] / drivers / visorbus / visorbus_main.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright � 2010 - 2015 UNISYS CORPORATION
 * All rights reserved.
 */

#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/visorbus.h>
#include <linux/uuid.h>

#include "visorbus_private.h"

static const guid_t visor_vbus_channel_guid = VISOR_VBUS_CHANNEL_GUID;

/* Display string that is guaranteed to be no longer the 99 characters */
#define LINESIZE 99
#define POLLJIFFIES_NORMALCHANNEL 10

/* stores whether bus_registration was successful */
static bool initialized;
static struct dentry *visorbus_debugfs_dir;

/*
 * DEVICE type attributes
 *
 * The modalias file will contain the guid of the device.
 */
static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct visor_device *vdev;
        const guid_t *guid;

        vdev = to_visor_device(dev);
        guid = visorchannel_get_guid(vdev->visorchannel);
        return sprintf(buf, "visorbus:%pUl\n", guid);
}
static DEVICE_ATTR_RO(modalias);

static struct attribute *visorbus_dev_attrs[] = {
        &dev_attr_modalias.attr,
        NULL,
};

ATTRIBUTE_GROUPS(visorbus_dev);

/* filled in with info about parent chipset driver when we register with it */
static struct visor_vbus_deviceinfo chipset_driverinfo;
/* filled in with info about this driver, wrt it servicing client busses */
static struct visor_vbus_deviceinfo clientbus_driverinfo;

/* list of visor_device structs, linked via .list_all */
static LIST_HEAD(list_all_bus_instances);
/* list of visor_device structs, linked via .list_all */
static LIST_HEAD(list_all_device_instances);

/*
 * Generic function useful for validating any type of channel when it is
 * received by the client that will be accessing the channel.
 * Note that <logCtx> is only needed for callers in the EFI environment, and
 * is used to pass the EFI_DIAG_CAPTURE_PROTOCOL needed to log messages.
 */
int visor_check_channel(struct channel_header *ch, struct device *dev,
                        const guid_t *expected_guid, char *chname,
                        u64 expected_min_bytes, u32 expected_version,
                        u64 expected_signature)
{
        if (!guid_is_null(expected_guid)) {
                /* caller wants us to verify type GUID */
                if (!guid_equal(&ch->chtype, expected_guid)) {
                        dev_err(dev, "Channel mismatch on channel=%s(%pUL) field=type expected=%pUL actual=%pUL\n",
                                chname, expected_guid, expected_guid,
                                &ch->chtype);
                        return 0;
                }
        }
        /* verify channel size */
        if (expected_min_bytes > 0) {
                if (ch->size < expected_min_bytes) {
                        dev_err(dev, "Channel mismatch on channel=%s(%pUL) field=size expected=0x%-8.8Lx actual=0x%-8.8Lx\n",
                                chname, expected_guid,
                                (unsigned long long)expected_min_bytes,
                                ch->size);
                        return 0;
                }
        }
        /* verify channel version */
        if (expected_version > 0) {
                if (ch->version_id != expected_version) {
                        dev_err(dev, "Channel mismatch on channel=%s(%pUL) field=version expected=0x%-8.8lx actual=0x%-8.8x\n",
                                chname, expected_guid,
                                (unsigned long)expected_version,
                                ch->version_id);
                        return 0;
                }
        }
        /* verify channel signature */
        if (expected_signature > 0) {
                if (ch->signature != expected_signature) {
                        dev_err(dev, "Channel mismatch on channel=%s(%pUL) field=signature expected=0x%-8.8Lx actual=0x%-8.8Lx\n",
                                chname, expected_guid,  expected_signature,
                                ch->signature);
                        return 0;
                }
        }
        return 1;
}

static int visorbus_uevent(struct device *xdev, struct kobj_uevent_env *env)
{
        struct visor_device *dev;
        const guid_t *guid;

        dev = to_visor_device(xdev);
        guid = visorchannel_get_guid(dev->visorchannel);
        return add_uevent_var(env, "MODALIAS=visorbus:%pUl", guid);
}

/*
 * visorbus_match() - called automatically upon adding a visor_device
 *                    (device_add), or adding a visor_driver
 *                    (visorbus_register_visor_driver)
 * @xdev: struct device for the device being matched
 * @xdrv: struct device_driver for driver to match device against
 *
 * Return: 1 iff the provided driver can control the specified device
 */
static int visorbus_match(struct device *xdev, struct device_driver *xdrv)
{
        const guid_t *channel_type;
        int i;
        struct visor_device *dev;
        struct visor_driver *drv;
        struct visorchannel *chan;

        dev = to_visor_device(xdev);
        channel_type = visorchannel_get_guid(dev->visorchannel);
        drv = to_visor_driver(xdrv);
        chan = dev->visorchannel;
        if (!drv->channel_types)
                return 0;
        for (i = 0; !guid_is_null(&drv->channel_types[i].guid); i++)
                if (guid_equal(&drv->channel_types[i].guid, channel_type) &&
                    visor_check_channel(visorchannel_get_header(chan),
                                        xdev,
                                        &drv->channel_types[i].guid,
                                        (char *)drv->channel_types[i].name,
                                        drv->channel_types[i].min_bytes,
                                        drv->channel_types[i].version,
                                        VISOR_CHANNEL_SIGNATURE))
                        return i + 1;
        return 0;
}

/*
 * This describes the TYPE of bus.
 * (Don't confuse this with an INSTANCE of the bus.)
 */
static struct bus_type visorbus_type = {
        .name = "visorbus",
        .match = visorbus_match,
        .uevent = visorbus_uevent,
        .dev_groups = visorbus_dev_groups,
};

struct visor_busdev {
        u32 bus_no;
        u32 dev_no;
};

static int match_visorbus_dev_by_id(struct device *dev, void *data)
{
        struct visor_device *vdev = to_visor_device(dev);
        struct visor_busdev *id = data;

        if (vdev->chipset_bus_no == id->bus_no &&
            vdev->chipset_dev_no == id->dev_no)
                return 1;
        return 0;
}

struct visor_device *visorbus_get_device_by_id(u32 bus_no, u32 dev_no,
                                               struct visor_device *from)
{
        struct device *dev;
        struct device *dev_start = NULL;
        struct visor_busdev id = {
                .bus_no = bus_no,
                .dev_no = dev_no
        };

        if (from)
                dev_start = &from->device;
        dev = bus_find_device(&visorbus_type, dev_start, (void *)&id,
                              match_visorbus_dev_by_id);
        if (!dev)
                return NULL;
        return to_visor_device(dev);
}

/*
 * visorbus_release_busdevice() - called when device_unregister() is called for
 *                                the bus device instance, after all other tasks
 *                                involved with destroying the dev are complete
 * @xdev: struct device for the bus being released
 */
static void visorbus_release_busdevice(struct device *xdev)
{
        struct visor_device *dev = dev_get_drvdata(xdev);

        debugfs_remove(dev->debugfs_bus_info);
        debugfs_remove_recursive(dev->debugfs_dir);
        visorchannel_destroy(dev->visorchannel);
        kfree(dev);
}

/*
 * visorbus_release_device() - called when device_unregister() is called for
 *                             each child device instance
 * @xdev: struct device for the visor device being released
 */
static void visorbus_release_device(struct device *xdev)
{
        struct visor_device *dev = to_visor_device(xdev);

        visorchannel_destroy(dev->visorchannel);
        kfree(dev);
}

/*
 * BUS specific channel attributes to appear under
 * /sys/bus/visorbus<x>/dev<y>/channel
 */

static ssize_t physaddr_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);

        return sprintf(buf, "0x%llx\n",
                       visorchannel_get_physaddr(vdev->visorchannel));
}
static DEVICE_ATTR_RO(physaddr);

static ssize_t nbytes_show(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);

        return sprintf(buf, "0x%lx\n",
                       visorchannel_get_nbytes(vdev->visorchannel));
}
static DEVICE_ATTR_RO(nbytes);

static ssize_t clientpartition_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);

        return sprintf(buf, "0x%llx\n",
                       visorchannel_get_clientpartition(vdev->visorchannel));
}
static DEVICE_ATTR_RO(clientpartition);

static ssize_t typeguid_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        char typeid[LINESIZE];

        return sprintf(buf, "%s\n",
                       visorchannel_id(vdev->visorchannel, typeid));
}
static DEVICE_ATTR_RO(typeguid);

static ssize_t zoneguid_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        char zoneid[LINESIZE];

        return sprintf(buf, "%s\n",
                       visorchannel_zoneid(vdev->visorchannel, zoneid));
}
static DEVICE_ATTR_RO(zoneguid);

static ssize_t typename_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        int i = 0;
        struct bus_type *xbus = dev->bus;
        struct device_driver *xdrv = dev->driver;
        struct visor_driver *drv = NULL;

        if (!xdrv)
                return 0;
        i = xbus->match(dev, xdrv);
        if (!i)
                return 0;
        drv = to_visor_driver(xdrv);
        return sprintf(buf, "%s\n", drv->channel_types[i - 1].name);
}
static DEVICE_ATTR_RO(typename);

static struct attribute *channel_attrs[] = {
        &dev_attr_physaddr.attr,
        &dev_attr_nbytes.attr,
        &dev_attr_clientpartition.attr,
        &dev_attr_typeguid.attr,
        &dev_attr_zoneguid.attr,
        &dev_attr_typename.attr,
        NULL
};

ATTRIBUTE_GROUPS(channel);

/*
 *  BUS instance attributes
 *
 *  define & implement display of bus attributes under
 *  /sys/bus/visorbus/devices/visorbus<n>.
 */
static ssize_t partition_handle_show(struct device *dev,
                                     struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        u64 handle = visorchannel_get_clientpartition(vdev->visorchannel);

        return sprintf(buf, "0x%llx\n", handle);
}
static DEVICE_ATTR_RO(partition_handle);

static ssize_t partition_guid_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);

        return sprintf(buf, "{%pUb}\n", &vdev->partition_guid);
}
static DEVICE_ATTR_RO(partition_guid);

static ssize_t partition_name_show(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);

        return sprintf(buf, "%s\n", vdev->name);
}
static DEVICE_ATTR_RO(partition_name);

static ssize_t channel_addr_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        u64 addr = visorchannel_get_physaddr(vdev->visorchannel);

        return sprintf(buf, "0x%llx\n", addr);
}
static DEVICE_ATTR_RO(channel_addr);

static ssize_t channel_bytes_show(struct device *dev,
                                  struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        u64 nbytes = visorchannel_get_nbytes(vdev->visorchannel);

        return sprintf(buf, "0x%llx\n", nbytes);
}
static DEVICE_ATTR_RO(channel_bytes);

static ssize_t channel_id_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct visor_device *vdev = to_visor_device(dev);
        int len = 0;

        visorchannel_id(vdev->visorchannel, buf);
        len = strlen(buf);
        buf[len++] = '\n';
        return len;
}
static DEVICE_ATTR_RO(channel_id);

static struct attribute *visorbus_attrs[] = {
        &dev_attr_partition_handle.attr,
        &dev_attr_partition_guid.attr,
        &dev_attr_partition_name.attr,
        &dev_attr_channel_addr.attr,
        &dev_attr_channel_bytes.attr,
        &dev_attr_channel_id.attr,
        NULL
};

ATTRIBUTE_GROUPS(visorbus);

/*
 *  BUS debugfs entries
 *
 *  define & implement display of debugfs attributes under
 *  /sys/kernel/debug/visorbus/visorbus<n>.
 */

/*
 * vbuschannel_print_devinfo() - format a struct visor_vbus_deviceinfo
 *                               and write it to a seq_file
 * @devinfo: the struct visor_vbus_deviceinfo to format
 * @seq: seq_file to write to
 * @devix: the device index to be included in the output data, or -1 if no
 *         device index is to be included
 *
 * Reads @devInfo, and writes it in human-readable notation to @seq.
 */
static void vbuschannel_print_devinfo(struct visor_vbus_deviceinfo *devinfo,
                                      struct seq_file *seq, int devix)
{
        /* uninitialized vbus device entry */
        if (!isprint(devinfo->devtype[0]))
                return;
        if (devix >= 0)
                seq_printf(seq, "[%d]", devix);
        else
                /* vbus device entry is for bus or chipset */
                seq_puts(seq, "   ");
        /*
         * Note: because the s-Par back-end is free to scribble in this area,
         * we never assume '\0'-termination.
         */
        seq_printf(seq, "%-*.*s ", (int)sizeof(devinfo->devtype),
                   (int)sizeof(devinfo->devtype), devinfo->devtype);
        seq_printf(seq, "%-*.*s ", (int)sizeof(devinfo->drvname),
                   (int)sizeof(devinfo->drvname), devinfo->drvname);
        seq_printf(seq, "%.*s\n", (int)sizeof(devinfo->infostrs),
                   devinfo->infostrs);
}

static int bus_info_debugfs_show(struct seq_file *seq, void *v)
{
        int i = 0;
        unsigned long off;
        struct visor_vbus_deviceinfo dev_info;
        struct visor_device *vdev = seq->private;
        struct visorchannel *channel = vdev->visorchannel;

        if (!channel)
                return 0;

        seq_printf(seq,
                   "Client device/driver info for %s partition (vbus #%u):\n",
                   ((vdev->name) ? (char *)(vdev->name) : ""),
                   vdev->chipset_bus_no);
        if (visorchannel_read(channel,
                              offsetof(struct visor_vbus_channel, chp_info),
                              &dev_info, sizeof(dev_info)) >= 0)
                vbuschannel_print_devinfo(&dev_info, seq, -1);
        if (visorchannel_read(channel,
                              offsetof(struct visor_vbus_channel, bus_info),
                              &dev_info, sizeof(dev_info)) >= 0)
                vbuschannel_print_devinfo(&dev_info, seq, -1);

        off = offsetof(struct visor_vbus_channel, dev_info);
        while (off + sizeof(dev_info) <= visorchannel_get_nbytes(channel)) {
                if (visorchannel_read(channel, off, &dev_info,
                                      sizeof(dev_info)) >= 0)
                        vbuschannel_print_devinfo(&dev_info, seq, i);
                off += sizeof(dev_info);
                i++;
        }
        return 0;
}

static int bus_info_debugfs_open(struct inode *inode, struct file *file)
{
        return single_open(file, bus_info_debugfs_show, inode->i_private);
}

static const struct file_operations bus_info_debugfs_fops = {
        .owner = THIS_MODULE,
        .open = bus_info_debugfs_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

static void dev_periodic_work(struct timer_list *t)
{
        struct visor_device *dev = from_timer(dev, t, timer);
        struct visor_driver *drv = to_visor_driver(dev->device.driver);

        drv->channel_interrupt(dev);
        mod_timer(&dev->timer, jiffies + POLLJIFFIES_NORMALCHANNEL);
}

static int dev_start_periodic_work(struct visor_device *dev)
{
        if (dev->being_removed || dev->timer_active)
                return -EINVAL;

        /* now up by at least 2 */
        get_device(&dev->device);
        dev->timer.expires = jiffies + POLLJIFFIES_NORMALCHANNEL;
        add_timer(&dev->timer);
        dev->timer_active = true;
        return 0;
}

static void dev_stop_periodic_work(struct visor_device *dev)
{
        if (!dev->timer_active)
                return;

        del_timer_sync(&dev->timer);
        dev->timer_active = false;
        put_device(&dev->device);
}

/*
 * visordriver_remove_device() - handle visor device going away
 * @xdev: struct device for the visor device being removed
 *
 * This is called when device_unregister() is called for each child device
 * instance, to notify the appropriate visorbus function driver that the device
 * is going away, and to decrease the reference count of the device.
 *
 * Return: 0 iff successful
 */
static int visordriver_remove_device(struct device *xdev)
{
        struct visor_device *dev = to_visor_device(xdev);
        struct visor_driver *drv = to_visor_driver(xdev->driver);

        mutex_lock(&dev->visordriver_callback_lock);
        dev->being_removed = true;
        drv->remove(dev);
        mutex_unlock(&dev->visordriver_callback_lock);
        dev_stop_periodic_work(dev);
        put_device(&dev->device);
        return 0;
}

/*
 * visorbus_unregister_visor_driver() - unregisters the provided driver
 * @drv: the driver to unregister
 *
 * A visor function driver calls this function to unregister the driver,
 * i.e., within its module_exit function.
 */
void visorbus_unregister_visor_driver(struct visor_driver *drv)
{
        driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(visorbus_unregister_visor_driver);

/*
 * visorbus_read_channel() - reads from the designated channel into
 *                           the provided buffer
 * @dev:    the device whose channel is read from
 * @offset: the offset into the channel at which reading starts
 * @dest:   the destination buffer that is written into from the channel
 * @nbytes: the number of bytes to read from the channel
 *
 * If receiving a message, use the visorchannel_signalremove() function instead.
 *
 * Return: integer indicating success (zero) or failure (non-zero)
 */
int visorbus_read_channel(struct visor_device *dev, unsigned long offset,
                          void *dest, unsigned long nbytes)
{
        return visorchannel_read(dev->visorchannel, offset, dest, nbytes);
}
EXPORT_SYMBOL_GPL(visorbus_read_channel);

/*
 * visorbus_write_channel() - writes the provided buffer into the designated
 *                            channel
 * @dev:    the device whose channel is written to
 * @offset: the offset into the channel at which writing starts
 * @src:    the source buffer that is written into the channel
 * @nbytes: the number of bytes to write into the channel
 *
 * If sending a message, use the visorchannel_signalinsert() function instead.
 *
 * Return: integer indicating success (zero) or failure (non-zero)
 */
int visorbus_write_channel(struct visor_device *dev, unsigned long offset,
                           void *src, unsigned long nbytes)
{
        return visorchannel_write(dev->visorchannel, offset, src, nbytes);
}
EXPORT_SYMBOL_GPL(visorbus_write_channel);

/*
 * visorbus_enable_channel_interrupts() - enables interrupts on the
 *                                        designated device
 * @dev: the device on which to enable interrupts
 *
 * Currently we don't yet have a real interrupt, so for now we just call the
 * interrupt function periodically via a timer.
 */
int visorbus_enable_channel_interrupts(struct visor_device *dev)
{
        struct visor_driver *drv = to_visor_driver(dev->device.driver);

        if (!drv->channel_interrupt) {
                dev_err(&dev->device, "%s no interrupt function!\n", __func__);
                return -ENOENT;
        }

        return dev_start_periodic_work(dev);
}
EXPORT_SYMBOL_GPL(visorbus_enable_channel_interrupts);

/*
 * visorbus_disable_channel_interrupts() - disables interrupts on the
 *                                         designated device
 * @dev: the device on which to disable interrupts
 */
void visorbus_disable_channel_interrupts(struct visor_device *dev)
{
        dev_stop_periodic_work(dev);
}
EXPORT_SYMBOL_GPL(visorbus_disable_channel_interrupts);

/*
 * create_visor_device() - create visor device as a result of receiving the
 *                         controlvm device_create message for a new device
 * @dev: a freshly-zeroed struct visor_device, containing only filled-in values
 *       for chipset_bus_no and chipset_dev_no, that will be initialized
 *
 * This is how everything starts from the device end.
 * This function is called when a channel first appears via a ControlVM
 * message.  In response, this function allocates a visor_device to correspond
 * to the new channel, and attempts to connect it the appropriate * driver. If
 * the appropriate driver is found, the visor_driver.probe() function for that
 * driver will be called, and will be passed the new * visor_device that we
 * just created.
 *
 * It's ok if the appropriate driver is not yet loaded, because in that case
 * the new device struct will just stick around in the bus' list of devices.
 * When the appropriate driver calls visorbus_register_visor_driver(), the
 * visor_driver.probe() for the new driver will be called with the new device.
 *
 * Return: 0 if successful, otherwise the negative value returned by
 *         device_add() indicating the reason for failure
 */
int create_visor_device(struct visor_device *dev)
{
        int err;
        u32 chipset_bus_no = dev->chipset_bus_no;
        u32 chipset_dev_no = dev->chipset_dev_no;

        mutex_init(&dev->visordriver_callback_lock);
        dev->device.bus = &visorbus_type;
        dev->device.groups = channel_groups;
        device_initialize(&dev->device);
        dev->device.release = visorbus_release_device;
        /* keep a reference just for us (now 2) */
        get_device(&dev->device);
        timer_setup(&dev->timer, dev_periodic_work, 0);
        /*
         * bus_id must be a unique name with respect to this bus TYPE (NOT bus
         * instance).  That's why we need to include the bus number within the
         * name.
         */
        err = dev_set_name(&dev->device, "vbus%u:dev%u",
                           chipset_bus_no, chipset_dev_no);
        if (err)
                goto err_put;
        /*
         * device_add does this:
         *    bus_add_device(dev)
         *    ->device_attach(dev)
         *      ->for each driver drv registered on the bus that dev is on
         *          if (dev.drv)  **  device already has a driver **
         *            ** not sure we could ever get here... **
         *          else
         *            if (bus.match(dev,drv)) [visorbus_match]
         *              dev.drv = drv
         *              if (!drv.probe(dev))  [visordriver_probe_device]
         *                dev.drv = NULL
         *
         * Note that device_add does NOT fail if no driver failed to claim the
         * device.  The device will be linked onto bus_type.klist_devices
         * regardless (use bus_for_each_dev).
         */
        err = device_add(&dev->device);
        if (err < 0)
                goto err_put;
        list_add_tail(&dev->list_all, &list_all_device_instances);
        dev->state.created = 1;
        visorbus_response(dev, err, CONTROLVM_DEVICE_CREATE);
        /* success: reference kept via unmatched get_device() */
        return 0;

err_put:
        put_device(&dev->device);
        dev_err(&dev->device, "Creating visor device failed. %d\n", err);
        return err;
}

void remove_visor_device(struct visor_device *dev)
{
        list_del(&dev->list_all);
        put_device(&dev->device);
        if (dev->pending_msg_hdr)
                visorbus_response(dev, 0, CONTROLVM_DEVICE_DESTROY);
        device_unregister(&dev->device);
}

static int get_vbus_header_info(struct visorchannel *chan,
                                struct device *dev,
                                struct visor_vbus_headerinfo *hdr_info)
{
        int err;

        if (!visor_check_channel(visorchannel_get_header(chan),
                                 dev,
                                 &visor_vbus_channel_guid,
                                 "vbus",
                                 sizeof(struct visor_vbus_channel),
                                 VISOR_VBUS_CHANNEL_VERSIONID,
                                 VISOR_CHANNEL_SIGNATURE))
                return -EINVAL;

        err = visorchannel_read(chan, sizeof(struct channel_header), hdr_info,
                                sizeof(*hdr_info));
        if (err < 0)
                return err;
        if (hdr_info->struct_bytes < sizeof(struct visor_vbus_headerinfo))
                return -EINVAL;
        if (hdr_info->device_info_struct_bytes <
            sizeof(struct visor_vbus_deviceinfo))
                return -EINVAL;
        return 0;
}

/*
 * write_vbus_chp_info() - write the contents of <info> to the struct
 *                         visor_vbus_channel.chp_info
 * @chan:     indentifies the s-Par channel that will be updated
 * @hdr_info: used to find appropriate channel offset to write data
 * @info:     contains the information to write
 *
 * Writes chipset info into the channel memory to be used for diagnostic
 * purposes.
 *
 * Returns no value since this is debug information and not needed for
 * device functionality.
 */
static void write_vbus_chp_info(struct visorchannel *chan,
                                struct visor_vbus_headerinfo *hdr_info,
                                struct visor_vbus_deviceinfo *info)
{
        int off;

        if (hdr_info->chp_info_offset == 0)
                return;

        off = sizeof(struct channel_header) + hdr_info->chp_info_offset;
        visorchannel_write(chan, off, info, sizeof(*info));
}

/*
 * write_vbus_bus_info() - write the contents of <info> to the struct
 *                         visor_vbus_channel.bus_info
 * @chan:     indentifies the s-Par channel that will be updated
 * @hdr_info: used to find appropriate channel offset to write data
 * @info:     contains the information to write
 *
 * Writes bus info into the channel memory to be used for diagnostic
 * purposes.
 *
 * Returns no value since this is debug information and not needed for
 * device functionality.
 */
static void write_vbus_bus_info(struct visorchannel *chan,
                                struct visor_vbus_headerinfo *hdr_info,
                                struct visor_vbus_deviceinfo *info)
{
        int off;

        if (hdr_info->bus_info_offset == 0)
                return;

        off = sizeof(struct channel_header) + hdr_info->bus_info_offset;
        visorchannel_write(chan, off, info, sizeof(*info));
}

/*
 * write_vbus_dev_info() - write the contents of <info> to the struct
 *                         visor_vbus_channel.dev_info[<devix>]
 * @chan:     indentifies the s-Par channel that will be updated
 * @hdr_info: used to find appropriate channel offset to write data
 * @info:     contains the information to write
 * @devix:    the relative device number (0..n-1) of the device on the bus
 *
 * Writes device info into the channel memory to be used for diagnostic
 * purposes.
 *
 * Returns no value since this is debug information and not needed for
 * device functionality.
 */
static void write_vbus_dev_info(struct visorchannel *chan,
                                struct visor_vbus_headerinfo *hdr_info,
                                struct visor_vbus_deviceinfo *info,
                                unsigned int devix)
{
        int off;

        if (hdr_info->dev_info_offset == 0)
                return;
        off = (sizeof(struct channel_header) + hdr_info->dev_info_offset) +
              (hdr_info->device_info_struct_bytes * devix);
        visorchannel_write(chan, off, info, sizeof(*info));
}

static void bus_device_info_init(
                struct visor_vbus_deviceinfo *bus_device_info_ptr,
                const char *dev_type, const char *drv_name)
{
        memset(bus_device_info_ptr, 0, sizeof(struct visor_vbus_deviceinfo));
        snprintf(bus_device_info_ptr->devtype,
                 sizeof(bus_device_info_ptr->devtype),
                 "%s", (dev_type) ? dev_type : "unknownType");
        snprintf(bus_device_info_ptr->drvname,
                 sizeof(bus_device_info_ptr->drvname),
                 "%s", (drv_name) ? drv_name : "unknownDriver");
        snprintf(bus_device_info_ptr->infostrs,
                 sizeof(bus_device_info_ptr->infostrs), "kernel ver. %s",
                 utsname()->release);
}

/*
 * publish_vbus_dev_info() - for a child device just created on a client bus,
 *                           fill in information about the driver that is
 *                           controlling this device into the appropriate slot
 *                           within the vbus channel of the bus instance
 * @visordev: struct visor_device for the desired device
 */
static void publish_vbus_dev_info(struct visor_device *visordev)
{
        int i;
        struct visor_device *bdev;
        struct visor_driver *visordrv;
        u32 bus_no = visordev->chipset_bus_no;
        u32 dev_no = visordev->chipset_dev_no;
        struct visor_vbus_deviceinfo dev_info;
        const char *chan_type_name = NULL;
        struct visor_vbus_headerinfo *hdr_info;

        if (!visordev->device.driver)
                return;
        bdev = visorbus_get_device_by_id(bus_no, BUS_ROOT_DEVICE, NULL);
        if (!bdev)
                return;
        hdr_info = (struct visor_vbus_headerinfo *)bdev->vbus_hdr_info;
        if (!hdr_info)
                return;
        visordrv = to_visor_driver(visordev->device.driver);

        /*
         * Within the list of device types (by GUID) that the driver
         * says it supports, find out which one of those types matches
         * the type of this device, so that we can include the device
         * type name
         */
        for (i = 0; visordrv->channel_types[i].name; i++) {
                if (guid_equal(&visordrv->channel_types[i].guid,
                               &visordev->channel_type_guid)) {
                        chan_type_name = visordrv->channel_types[i].name;
                        break;
                }
        }
        bus_device_info_init(&dev_info, chan_type_name, visordrv->name);
        write_vbus_dev_info(bdev->visorchannel, hdr_info, &dev_info, dev_no);
        write_vbus_chp_info(bdev->visorchannel, hdr_info, &chipset_driverinfo);
        write_vbus_bus_info(bdev->visorchannel, hdr_info,
                            &clientbus_driverinfo);
}

/*
 * visordriver_probe_device() - handle new visor device coming online
 * @xdev: struct device for the visor device being probed
 *
 * This is called automatically upon adding a visor_device (device_add), or
 * adding a visor_driver (visorbus_register_visor_driver), but only after
 * visorbus_match() has returned 1 to indicate a successful match between
 * driver and device.
 *
 * If successful, a reference to the device will be held onto via get_device().
 *
 * Return: 0 if successful, meaning the function driver's probe() function
 *         was successful with this device, otherwise a negative errno
 *         value indicating failure reason
 */
static int visordriver_probe_device(struct device *xdev)
{
        int err;
        struct visor_driver *drv = to_visor_driver(xdev->driver);
        struct visor_device *dev = to_visor_device(xdev);

        mutex_lock(&dev->visordriver_callback_lock);
        dev->being_removed = false;
        err = drv->probe(dev);
        if (err) {
                mutex_unlock(&dev->visordriver_callback_lock);
                return err;
        }
        /* success: reference kept via unmatched get_device() */
        get_device(&dev->device);
        publish_vbus_dev_info(dev);
        mutex_unlock(&dev->visordriver_callback_lock);
        return 0;
}

/*
 * visorbus_register_visor_driver() - registers the provided visor driver for
 *                                    handling one or more visor device
 *                                    types (channel_types)
 * @drv: the driver to register
 *
 * A visor function driver calls this function to register the driver. The
 * caller MUST fill in the following fields within the #drv structure:
 *     name, version, owner, channel_types, probe, remove
 *
 * Here's how the whole Linux bus / driver / device model works.
 *
 * At system start-up, the visorbus kernel module is loaded, which registers
 * visorbus_type as a bus type, using bus_register().
 *
 * All kernel modules that support particular device types on a
 * visorbus bus are loaded.  Each of these kernel modules calls
 * visorbus_register_visor_driver() in their init functions, passing a
 * visor_driver struct.  visorbus_register_visor_driver() in turn calls
 * register_driver(&visor_driver.driver).  This .driver member is
 * initialized with generic methods (like probe), whose sole responsibility
 * is to act as a broker for the real methods, which are within the
 * visor_driver struct.  (This is the way the subclass behavior is
 * implemented, since visor_driver is essentially a subclass of the
 * generic driver.)  Whenever a driver_register() happens, core bus code in
 * the kernel does (see device_attach() in drivers/base/dd.c):
 *
 *     for each dev associated with the bus (the bus that driver is on) that
 *     does not yet have a driver
 *         if bus.match(dev,newdriver) == yes_matched  ** .match specified
 *                                                ** during bus_register().
 *             newdriver.probe(dev)  ** for visor drivers, this will call
 *                   ** the generic driver.probe implemented in visorbus.c,
 *                   ** which in turn calls the probe specified within the
 *                   ** struct visor_driver (which was specified by the
 *                   ** actual device driver as part of
 *                   ** visorbus_register_visor_driver()).
 *
 * The above dance also happens when a new device appears.
 * So the question is, how are devices created within the system?
 * Basically, just call device_add(dev).  See pci_bus_add_devices().
 * pci_scan_device() shows an example of how to build a device struct.  It
 * returns the newly-created struct to pci_scan_single_device(), who adds it
 * to the list of devices at PCIBUS.devices.  That list of devices is what
 * is traversed by pci_bus_add_devices().
 *
 * Return: integer indicating success (zero) or failure (non-zero)
 */
int visorbus_register_visor_driver(struct visor_driver *drv)
{
        /* can't register on a nonexistent bus */
        if (!initialized)
                return -ENODEV;
        if (!drv->probe)
                return -EINVAL;
        if (!drv->remove)
                return -EINVAL;
        if (!drv->pause)
                return -EINVAL;
        if (!drv->resume)
                return -EINVAL;

        drv->driver.name = drv->name;
        drv->driver.bus = &visorbus_type;
        drv->driver.probe = visordriver_probe_device;
        drv->driver.remove = visordriver_remove_device;
        drv->driver.owner = drv->owner;
        /*
         * driver_register does this:
         *   bus_add_driver(drv)
         *   ->if (drv.bus)  ** (bus_type) **
         *       driver_attach(drv)
         *         for each dev with bus type of drv.bus
         *           if (!dev.drv)  ** no driver assigned yet **
         *             if (bus.match(dev,drv))  [visorbus_match]
         *               dev.drv = drv
         *               if (!drv.probe(dev))   [visordriver_probe_device]
         *                 dev.drv = NULL
         */
        return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(visorbus_register_visor_driver);

/*
 * visorbus_create_instance() - create a device instance for the visorbus itself
 * @dev: struct visor_device indicating the bus instance
 *
 * Return: 0 for success, otherwise negative errno value indicating reason for
 *         failure
 */
int visorbus_create_instance(struct visor_device *dev)
{
        int id = dev->chipset_bus_no;
        int err;
        struct visor_vbus_headerinfo *hdr_info;

        hdr_info = kzalloc(sizeof(*hdr_info), GFP_KERNEL);
        if (!hdr_info)
                return -ENOMEM;
        dev_set_name(&dev->device, "visorbus%d", id);
        dev->device.bus = &visorbus_type;
        dev->device.groups = visorbus_groups;
        dev->device.release = visorbus_release_busdevice;
        dev->debugfs_dir = debugfs_create_dir(dev_name(&dev->device),
                                              visorbus_debugfs_dir);
        dev->debugfs_bus_info = debugfs_create_file("client_bus_info", 0440,
                                                    dev->debugfs_dir, dev,
                                                    &bus_info_debugfs_fops);
        dev_set_drvdata(&dev->device, dev);
        err = get_vbus_header_info(dev->visorchannel, &dev->device, hdr_info);
        if (err < 0)
                goto err_debugfs_dir;
        err = device_register(&dev->device);
        if (err < 0)
                goto err_debugfs_dir;
        list_add_tail(&dev->list_all, &list_all_bus_instances);
        dev->state.created = 1;
        dev->vbus_hdr_info = (void *)hdr_info;
        write_vbus_chp_info(dev->visorchannel, hdr_info, &chipset_driverinfo);
        write_vbus_bus_info(dev->visorchannel, hdr_info, &clientbus_driverinfo);
        visorbus_response(dev, err, CONTROLVM_BUS_CREATE);
        return 0;

err_debugfs_dir:
        debugfs_remove_recursive(dev->debugfs_dir);
        kfree(hdr_info);
        dev_err(&dev->device, "%s failed: %d\n", __func__, err);
        return err;
}

/*
 * visorbus_remove_instance() - remove a device instance for the visorbus itself
 * @dev: struct visor_device indentifying the bus to remove
 */
void visorbus_remove_instance(struct visor_device *dev)
{
        /*
         * Note that this will result in the release method for
         * dev->dev being called, which will call
         * visorbus_release_busdevice().  This has something to do with
         * the put_device() done in device_unregister(), but I have never
         * successfully been able to trace thru the code to see where/how
         * release() gets called.  But I know it does.
         */
        kfree(dev->vbus_hdr_info);
        list_del(&dev->list_all);
        if (dev->pending_msg_hdr)
                visorbus_response(dev, 0, CONTROLVM_BUS_DESTROY);
        device_unregister(&dev->device);
}

/*
 * remove_all_visor_devices() - remove all child visorbus device instances
 */
static void remove_all_visor_devices(void)
{
        struct list_head *listentry, *listtmp;

        list_for_each_safe(listentry, listtmp, &list_all_device_instances) {
                struct visor_device *dev;

                dev = list_entry(listentry, struct visor_device, list_all);
                remove_visor_device(dev);
        }
}

/*
 * pause_state_change_complete() - the callback function to be called by a
 *                                 visorbus function driver when a
 *                                 pending "pause device" operation has
 *                                 completed
 * @dev: struct visor_device identifying the paused device
 * @status: 0 iff the pause state change completed successfully, otherwise
 *          a negative errno value indicating the reason for failure
 */
static void pause_state_change_complete(struct visor_device *dev, int status)
{
        if (!dev->pausing)
                return;

        dev->pausing = false;
        visorbus_device_changestate_response(dev, status,
                                             segment_state_standby);
}

/*
 * resume_state_change_complete() - the callback function to be called by a
 *                                  visorbus function driver when a
 *                                  pending "resume device" operation has
 *                                  completed
 * @dev: struct visor_device identifying the resumed device
 * @status: 0 iff the resume state change completed successfully, otherwise
 *          a negative errno value indicating the reason for failure
 */
static void resume_state_change_complete(struct visor_device *dev, int status)
{
        if (!dev->resuming)
                return;

        dev->resuming = false;
        /*
         * Notify the chipset driver that the resume is complete,
         * which will presumably want to send some sort of response to
         * the initiator.
         */
        visorbus_device_changestate_response(dev, status,
                                             segment_state_running);
}

/*
 * visorchipset_initiate_device_pause_resume() - start a pause or resume
 *                                               operation for a visor device
 * @dev: struct visor_device identifying the device being paused or resumed
 * @is_pause: true to indicate pause operation, false to indicate resume
 *
 * Tell the subordinate function driver for a specific device to pause
 * or resume that device.  Success/failure result is returned asynchronously
 * via a callback function; see pause_state_change_complete() and
 * resume_state_change_complete().
 */
static int visorchipset_initiate_device_pause_resume(struct visor_device *dev,
                                                     bool is_pause)
{
        int err;
        struct visor_driver *drv;

        /* If no driver associated with the device nothing to pause/resume */
        if (!dev->device.driver)
                return 0;
        if (dev->pausing || dev->resuming)
                return -EBUSY;

        drv = to_visor_driver(dev->device.driver);
        if (is_pause) {
                dev->pausing = true;
                err = drv->pause(dev, pause_state_change_complete);
        } else {
                /*
                 * The vbus_dev_info structure in the channel was been cleared,
                 * make sure it is valid.
                 */
                publish_vbus_dev_info(dev);
                dev->resuming = true;
                err = drv->resume(dev, resume_state_change_complete);
        }
        return err;
}

/*
 * visorchipset_device_pause() - start a pause operation for a visor device
 * @dev_info: struct visor_device identifying the device being paused
 *
 * Tell the subordinate function driver for a specific device to pause
 * that device.  Success/failure result is returned asynchronously
 * via a callback function; see pause_state_change_complete().
 */
int visorchipset_device_pause(struct visor_device *dev_info)
{
        int err;

        err = visorchipset_initiate_device_pause_resume(dev_info, true);
        if (err < 0) {
                dev_info->pausing = false;
                return err;
        }
        return 0;
}

/*
 * visorchipset_device_resume() - start a resume operation for a visor device
 * @dev_info: struct visor_device identifying the device being resumed
 *
 * Tell the subordinate function driver for a specific device to resume
 * that device.  Success/failure result is returned asynchronously
 * via a callback function; see resume_state_change_complete().
 */
int visorchipset_device_resume(struct visor_device *dev_info)
{
        int err;

        err = visorchipset_initiate_device_pause_resume(dev_info, false);
        if (err < 0) {
                dev_info->resuming = false;
                return err;
        }
        return 0;
}

int visorbus_init(void)
{
        int err;

        visorbus_debugfs_dir = debugfs_create_dir("visorbus", NULL);
        bus_device_info_init(&clientbus_driverinfo, "clientbus", "visorbus");
        err = bus_register(&visorbus_type);
        if (err < 0)
                return err;
        initialized = true;
        bus_device_info_init(&chipset_driverinfo, "chipset", "visorchipset");
        return 0;
}

void visorbus_exit(void)
{
        struct list_head *listentry, *listtmp;

        remove_all_visor_devices();
        list_for_each_safe(listentry, listtmp, &list_all_bus_instances) {
                struct visor_device *dev;

                dev = list_entry(listentry, struct visor_device, list_all);
                visorbus_remove_instance(dev);
        }
        bus_unregister(&visorbus_type);
        initialized = false;
        debugfs_remove_recursive(visorbus_debugfs_dir);
}