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