1 files changed, 207 insertions, 0 deletions

diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
new file mode 100644
index 000000000000..313da35984af
--- /dev/null
+++ b/drivers/uio/uio_pci_generic.c
@@ -0,0 +1,207 @@
+/* uio_pci_generic - generic UIO driver for PCI 2.3 devices
+ *
+ * Copyright (C) 2009 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Since the driver does not declare any device ids, you must allocate
+ * id and bind the device to the driver yourself.  For example:
+ *
+ * # echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
+ * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
+ * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/uio_pci_generic/bind
+ * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
+ * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
+ *
+ * Driver won't bind to devices which do not support the Interrupt Disable Bit
+ * in the command register. All devices compliant to PCI 2.3 (circa 2002) and
+ * all compliant PCI Express devices should support this bit.
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/uio_driver.h>
+#include <linux/spinlock.h>
+
+#define DRIVER_VERSION  "0.01.0"
+#define DRIVER_AUTHOR   "Michael S. Tsirkin <mst@redhat.com>"
+#define DRIVER_DESC     "Generic UIO driver for PCI 2.3 devices"
+
+struct uio_pci_generic_dev {
+        struct uio_info info;
+        struct pci_dev *pdev;
+        spinlock_t lock; /* guards command register accesses */
+};
+
+static inline struct uio_pci_generic_dev *
+to_uio_pci_generic_dev(struct uio_info *info)
+{
+        return container_of(info, struct uio_pci_generic_dev, info);
+}
+
+/* Interrupt handler. Read/modify/write the command register to disable
+ * the interrupt. */
+static irqreturn_t irqhandler(int irq, struct uio_info *info)
+{
+        struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
+        struct pci_dev *pdev = gdev->pdev;
+        irqreturn_t ret = IRQ_NONE;
+        u32 cmd_status_dword;
+        u16 origcmd, newcmd, status;
+
+        /* We do a single dword read to retrieve both command and status.
+         * Document assumptions that make this possible. */
+        BUILD_BUG_ON(PCI_COMMAND % 4);
+        BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
+
+        spin_lock_irq(&gdev->lock);
+        pci_block_user_cfg_access(pdev);
+
+        /* Read both command and status registers in a single 32-bit operation.
+         * Note: we could cache the value for command and move the status read
+         * out of the lock if there was a way to get notified of user changes
+         * to command register through sysfs. Should be good for shared irqs. */
+        pci_read_config_dword(pdev, PCI_COMMAND, &cmd_status_dword);
+        origcmd = cmd_status_dword;
+        status = cmd_status_dword >> 16;
+
+        /* Check interrupt status register to see whether our device
+         * triggered the interrupt. */
+        if (!(status & PCI_STATUS_INTERRUPT))
+                goto done;
+
+        /* We triggered the interrupt, disable it. */
+        newcmd = origcmd | PCI_COMMAND_INTX_DISABLE;
+        if (newcmd != origcmd)
+                pci_write_config_word(pdev, PCI_COMMAND, newcmd);
+
+        /* UIO core will signal the user process. */
+        ret = IRQ_HANDLED;
+done:
+
+        pci_unblock_user_cfg_access(pdev);
+        spin_unlock_irq(&gdev->lock);
+        return ret;
+}
+
+/* Verify that the device supports Interrupt Disable bit in command register,
+ * per PCI 2.3, by flipping this bit and reading it back: this bit was readonly
+ * in PCI 2.2. */
+static int __devinit verify_pci_2_3(struct pci_dev *pdev)
+{
+        u16 orig, new;
+        int err = 0;
+
+        pci_block_user_cfg_access(pdev);
+        pci_read_config_word(pdev, PCI_COMMAND, &orig);
+        pci_write_config_word(pdev, PCI_COMMAND,
+                              orig ^ PCI_COMMAND_INTX_DISABLE);
+        pci_read_config_word(pdev, PCI_COMMAND, &new);
+        /* There's no way to protect against
+         * hardware bugs or detect them reliably, but as long as we know
+         * what the value should be, let's go ahead and check it. */
+        if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
+                err = -EBUSY;
+                dev_err(&pdev->dev, "Command changed from 0x%x to 0x%x: "
+                        "driver or HW bug?\n", orig, new);
+                goto err;
+        }
+        if (!((new ^ orig) & PCI_COMMAND_INTX_DISABLE)) {
+                dev_warn(&pdev->dev, "Device does not support "
+                         "disabling interrupts: unable to bind.\n");
+                err = -ENODEV;
+                goto err;
+        }
+        /* Now restore the original value. */
+        pci_write_config_word(pdev, PCI_COMMAND, orig);
+err:
+        pci_unblock_user_cfg_access(pdev);
+        return err;
+}
+
+static int __devinit probe(struct pci_dev *pdev,
+                           const struct pci_device_id *id)
+{
+        struct uio_pci_generic_dev *gdev;
+        int err;
+
+        if (!pdev->irq) {
+                dev_warn(&pdev->dev, "No IRQ assigned to device: "
+                         "no support for interrupts?\n");
+                return -ENODEV;
+        }
+
+        err = pci_enable_device(pdev);
+        if (err) {
+                dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
+                        __func__, err);
+                return err;
+        }
+
+        err = verify_pci_2_3(pdev);
+        if (err)
+                goto err_verify;
+
+        gdev = kzalloc(sizeof(struct uio_pci_generic_dev), GFP_KERNEL);
+        if (!gdev) {
+                err = -ENOMEM;
+                goto err_alloc;
+        }
+
+        gdev->info.name = "uio_pci_generic";
+        gdev->info.version = DRIVER_VERSION;
+        gdev->info.irq = pdev->irq;
+        gdev->info.irq_flags = IRQF_SHARED;
+        gdev->info.handler = irqhandler;
+        gdev->pdev = pdev;
+        spin_lock_init(&gdev->lock);
+
+        if (uio_register_device(&pdev->dev, &gdev->info))
+                goto err_register;
+        pci_set_drvdata(pdev, gdev);
+
+        return 0;
+err_register:
+        kfree(gdev);
+err_alloc:
+err_verify:
+        pci_disable_device(pdev);
+        return err;
+}
+
+static void remove(struct pci_dev *pdev)
+{
+        struct uio_pci_generic_dev *gdev = pci_get_drvdata(pdev);
+
+        uio_unregister_device(&gdev->info);
+        pci_disable_device(pdev);
+        kfree(gdev);
+}
+
+static struct pci_driver driver = {
+        .name = "uio_pci_generic",
+        .id_table = NULL, /* only dynamic id's */
+        .probe = probe,
+        .remove = remove,
+};
+
+static int __init init(void)
+{
+        pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
+        return pci_register_driver(&driver);
+}
+
+static void __exit cleanup(void)
+{
+        pci_unregister_driver(&driver);
+}
+
+module_init(init);
+module_exit(cleanup);
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);