<year>2006-2008</year>
<holder>Hans-Jürgen Koch.</holder>
</copyright>
+<copyright>
+ <year>2009</year>
+ <holder>Red Hat Inc, Michael S. Tsirkin (mst@redhat.com)</holder>
+</copyright>
<legalnotice>
<para>
<revhistory>
<revision>
+ <revnumber>0.9</revnumber>
+ <date>2009-07-16</date>
+ <authorinitials>mst</authorinitials>
+ <revremark>Added generic pci driver
+ </revremark>
+ </revision>
+ <revision>
<revnumber>0.8</revnumber>
<date>2008-12-24</date>
<authorinitials>hjk</authorinitials>
</chapter>
+<chapter id="uio_pci_generic" xreflabel="Using Generic driver for PCI cards">
+<?dbhtml filename="uio_pci_generic.html"?>
+<title>Generic PCI UIO driver</title>
+ <para>
+ The generic driver is a kernel module named uio_pci_generic.
+ It can work with any device compliant to PCI 2.3 (circa 2002) and
+ any compliant PCI Express device. Using this, you only need to
+ write the userspace driver, removing the need to write
+ a hardware-specific kernel module.
+ </para>
+
+<sect1 id="uio_pci_generic_binding">
+<title>Making the driver recognize the device</title>
+ <para>
+Since the driver does not declare any device ids, it will not get loaded
+automatically and will not automatically bind to any devices, you must load it
+and allocate id to the driver yourself. For example:
+ <programlisting>
+ modprobe uio_pci_generic
+ echo "8086 10f5" > /sys/bus/pci/drivers/uio_pci_generic/new_id
+ </programlisting>
+ </para>
+ <para>
+If there already is a hardware specific kernel driver for your device, the
+generic driver still won't bind to it, in this case if you want to use the
+generic driver (why would you?) you'll have to manually unbind the hardware
+specific driver and bind the generic driver, like this:
+ <programlisting>
+ 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
+ </programlisting>
+ </para>
+ <para>
+You can verify that the device has been bound to the driver
+by looking for it in sysfs, for example like the following:
+ <programlisting>
+ ls -l /sys/bus/pci/devices/0000:00:19.0/driver
+ </programlisting>
+Which if successful should print
+ <programlisting>
+ .../0000:00:19.0/driver -> ../../../bus/pci/drivers/uio_pci_generic
+ </programlisting>
+Note that the generic driver will not bind to old PCI 2.2 devices.
+If binding the device failed, run the following command:
+ <programlisting>
+ dmesg
+ </programlisting>
+and look in the output for failure reasons
+ </para>
+</sect1>
+
+<sect1 id="uio_pci_generic_internals">
+<title>Things to know about uio_pci_generic</title>
+ <para>
+Interrupts are handled using the Interrupt Disable bit in the PCI command
+register and Interrupt Status bit in the PCI status register. All devices
+compliant to PCI 2.3 (circa 2002) and all compliant PCI Express devices should
+support these bits. uio_pci_generic detects this support, and won't bind to
+devices which do not support the Interrupt Disable Bit in the command register.
+ </para>
+ <para>
+On each interrupt, uio_pci_generic sets the Interrupt Disable bit.
+This prevents the device from generating further interrupts
+until the bit is cleared. The userspace driver should clear this
+bit before blocking and waiting for more interrupts.
+ </para>
+</sect1>
+<sect1 id="uio_pci_generic_userspace">
+<title>Writing userspace driver using uio_pci_generic</title>
+ <para>
+Userspace driver can use pci sysfs interface, or the
+libpci libray that wraps it, to talk to the device and to
+re-enable interrupts by writing to the command register.
+ </para>
+</sect1>
+<sect1 id="uio_pci_generic_example">
+<title>Example code using uio_pci_generic</title>
+ <para>
+Here is some sample userspace driver code using uio_pci_generic:
+<programlisting>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+int main()
+{
+ int uiofd;
+ int configfd;
+ int err;
+ int i;
+ unsigned icount;
+ unsigned char command_high;
+
+ uiofd = open("/dev/uio0", O_RDONLY);
+ if (uiofd < 0) {
+ perror("uio open:");
+ return errno;
+ }
+ configfd = open("/sys/class/uio/uio0/device/config", O_RDWR);
+ if (uiofd < 0) {
+ perror("config open:");
+ return errno;
+ }
+
+ /* Read and cache command value */
+ err = pread(configfd, &command_high, 1, 5);
+ if (err != 1) {
+ perror("command config read:");
+ return errno;
+ }
+ command_high &= ~0x4;
+
+ for(i = 0;; ++i) {
+ /* Print out a message, for debugging. */
+ if (i == 0)
+ fprintf(stderr, "Started uio test driver.\n");
+ else
+ fprintf(stderr, "Interrupts: %d\n", icount);
+
+ /****************************************/
+ /* Here we got an interrupt from the
+ device. Do something to it. */
+ /****************************************/
+
+ /* Re-enable interrupts. */
+ err = pwrite(configfd, &command_high, 1, 5);
+ if (err != 1) {
+ perror("config write:");
+ break;
+ }
+
+ /* Wait for next interrupt. */
+ err = read(uiofd, &icount, 4);
+ if (err != 4) {
+ perror("uio read:");
+ break;
+ }
+
+ }
+ return errno;
+}
+
+</programlisting>
+ </para>
+</sect1>
+
+</chapter>
+
<appendix id="app1">
<title>Further information</title>
<itemizedlist>
--- /dev/null
+/* 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);
projects / platform / kernel / kernel-mfld-blackbay.git / commitdiff