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