drivers/uio/uio_pci_generic.c

   1 /* uio_pci_generic - generic UIO driver for PCI 2.3 devices
   2  *
   3  * Copyright (C) 2009 Red Hat, Inc.
   4  * Author: Michael S. Tsirkin <mst@redhat.com>
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2.
   7  *
   8  * Since the driver does not declare any device ids, you must allocate
   9  * id and bind the device to the driver yourself.  For example:
  10  *
  11  * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
  12  * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
  13  * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
  14  * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
  15  * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
  16  *
  17  * Driver won't bind to devices which do not support the Interrupt Disable Bit
  18  * in the command register. All devices compliant to PCI 2.3 (circa 2002) and
  19  * all compliant PCI Express devices should support this bit.
  20  */
  21
  22 #include <linux/device.h>
  23 #include <linux/module.h>
  24 #include <linux/pci.h>
  25 #include <linux/slab.h>
  26 #include <linux/uio_driver.h>
  27 #include <linux/spinlock.h>
  28
  29 #define DRIVER_VERSION  "0.01.0"
  30 #define DRIVER_AUTHOR   "Michael S. Tsirkin <mst@redhat.com>"
  31 #define DRIVER_DESC     "Generic UIO driver for PCI 2.3 devices"
  32
  33 struct uio_pci_generic_dev {
  34         struct uio_info info;
  35         struct pci_dev *pdev;
  36         spinlock_t lock; /* guards command register accesses */
  37 };
  38
  39 static inline struct uio_pci_generic_dev *
  40 to_uio_pci_generic_dev(struct uio_info *info)
  41 {
  42         return container_of(info, struct uio_pci_generic_dev, info);
  43 }
  44
  45 /* Interrupt handler. Read/modify/write the command register to disable
  46  * the interrupt. */
  47 static irqreturn_t irqhandler(int irq, struct uio_info *info)
  48 {
  49         struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
  50         struct pci_dev *pdev = gdev->pdev;
  51         irqreturn_t ret = IRQ_NONE;
  52         u32 cmd_status_dword;
  53         u16 origcmd, newcmd, status;
  54
  55         /* We do a single dword read to retrieve both command and status.
  56          * Document assumptions that make this possible. */
  57         BUILD_BUG_ON(PCI_COMMAND % 4);
  58         BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
  59
  60         spin_lock_irq(&gdev->lock);
  61         pci_block_user_cfg_access(pdev);
  62
  63         /* Read both command and status registers in a single 32-bit operation.
  64          * Note: we could cache the value for command and move the status read
  65          * out of the lock if there was a way to get notified of user changes
  66          * to command register through sysfs. Should be good for shared irqs. */
  67         pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword);
  68         origcmd = cmd_status_dword;
  69         status = cmd_status_dword >> 16;
  70
  71         /* Check interrupt status register to see whether our device
  72          * triggered the interrupt. */
  73         if (!(status & PCI_STATUS_INTERRUPT))
  74                 goto done;
  75
  76         /* We triggered the interrupt, disable it. */
  77         newcmd = origcmd | PCI_COMMAND_INTX_DISABLE;
  78         if (newcmd != origcmd)
  79                 pci_write_config_word(pdev, PCI_COMMAND, newcmd);
  80
  81         /* UIO core will signal the user process. */
  82         ret = IRQ_HANDLED;
  83 done:
  84
  85         pci_unblock_user_cfg_access(pdev);
  86         spin_unlock_irq(&gdev->lock);
  87         return ret;
  88 }
  89
  90 /* Verify that the device supports Interrupt Disable bit in command register,
  91  * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly
  92  * in PCI 2.2. */
  93 static int __devinit verify_pci_2_3(struct pci_dev *pdev)
  94 {
  95         u16 orig, new;
  96         int err = 0;
  97
  98         pci_block_user_cfg_access(pdev);
  99         pci_read_config_word(pdev, PCI_COMMAND, &orig);
 100         pci_write_config_word(pdev, PCI_COMMAND,
 101                               orig ^ PCI_COMMAND_INTX_DISABLE);
 102         pci_read_config_word(pdev, PCI_COMMAND, &new);
 103         /* There's no way to protect against
 104          * hardware bugs or detect them reliably, but as long as we know
 105          * what the value should be, let's go ahead and check it. */
 106         if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
 107                 err = -EBUSY;
 108                 dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: "
 109                         "driver or HW bug?\n", orig, new);
 110                 goto err;
 111         }
 112         if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) {
 113                 dev_warn(&pdev->dev, "Device does not support "
 114                          "disabling interrupts: unable to bind.\n");
 115                 err = -ENODEV;
 116                 goto err;
 117         }
 118         /* Now restore the original value. */
 119         pci_write_config_word(pdev, PCI_COMMAND, orig);
 120 err:
 121         pci_unblock_user_cfg_access(pdev);
 122         return err;
 123 }
 124
 125 static int __devinit probe(struct pci_dev *pdev,
 126                            const struct pci_device_id *id)
 127 {
 128         struct uio_pci_generic_dev *gdev;
 129         int err;
 130
 131         err = pci_enable_device(pdev);
 132         if (err) {
 133                 dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
 134                         __func__, err);
 135                 return err;
 136         }
 137
 138         if (!pdev->irq) {
 139                 dev_warn(&pdev->dev, "No IRQ assigned to device: "
 140                          "no support for interrupts?\n");
 141                 pci_disable_device(pdev);
 142                 return -ENODEV;
 143         }
 144
 145         err = verify_pci_2_3(pdev);
 146         if (err)
 147                 goto err_verify;
 148
 149         gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
 150         if (!gdev) {
 151                 err = -ENOMEM;
 152                 goto err_alloc;
 153         }
 154
 155         gdev->info.name = "uio_pci_generic";
 156         gdev->info.version = DRIVER_VERSION;
 157         gdev->info.irq = pdev->irq;
 158         gdev->info.irq_flags = IRQF_SHARED;
 159         gdev->info.handler = irqhandler;
 160         gdev->pdev = pdev;
 161         spin_lock_init(&gdev->lock);
 162
 163         if (uio_register_device(&pdev->dev, &gdev->info))
 164                 goto err_register;
 165         pci_set_drvdata(pdev, gdev);
 166
 167         return 0;
 168 err_register:
 169         kfree(gdev);
 170 err_alloc:
 171 err_verify:
 172         pci_disable_device(pdev);
 173         return err;
 174 }
 175
 176 static void remove(struct pci_dev *pdev)
 177 {
 178         struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
 179
 180         uio_unregister_device(&gdev->info);
 181         pci_disable_device(pdev);
 182         kfree(gdev);
 183 }
 184
 185 static struct pci_driver driver = {
 186         .name = "uio_pci_generic",
 187         .id_table = NULL, /* only dynamic id's */
 188         .probe = probe,
 189         .remove = remove,
 190 };
 191
 192 static int __init init(void)
 193 {
 194         pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
 195         return pci_register_driver(&driver);
 196 }
 197
 198 static void __exit cleanup(void)
 199 {
 200         pci_unregister_driver(&driver);
 201 }
 202
 203 module_init(init);
 204 module_exit(cleanup);
 205
 206 MODULE_VERSION(DRIVER_VERSION);
 207 MODULE_LICENSE("GPL v2");
 208 MODULE_AUTHOR(DRIVER_AUTHOR);
 209 MODULE_DESCRIPTION(DRIVER_DESC);