6 files changed, 389 insertions, 0 deletions

diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl
index 8f6e3b2403c7..4d4ce0e61e42 100644
--- a/Documentation/DocBook/uio-howto.tmpl
+++ b/Documentation/DocBook/uio-howto.tmpl
@@ -25,6 +25,10 @@
         <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>
@@ -42,6 +46,13 @@ GPL version 2.
 
 <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>
@@ -809,6 +820,158 @@ framework to set up sysfs files for this region. Simply leave it alone.
 
 </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 &quot;8086 10f5&quot; &gt; /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 &gt; /sys/bus/pci/drivers/e1000e/unbind
+    echo -n 0000:00:19.0 &gt; /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 -&gt; ../../../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 &lt;stdlib.h&gt;
+#include &lt;stdio.h&gt;
+#include &lt;unistd.h&gt;
+#include &lt;sys/types.h&gt;
+#include &lt;sys/stat.h&gt;
+#include &lt;fcntl.h&gt;
+#include &lt;errno.h&gt;
+
+int main()
+{
+        int uiofd;
+        int configfd;
+        int err;
+        int i;
+        unsigned icount;
+        unsigned char command_high;
+
+        uiofd = open(&quot;/dev/uio0&quot;, O_RDONLY);
+        if (uiofd &lt; 0) {
+                perror(&quot;uio open:&quot;);
+                return errno;
+        }
+        configfd = open(&quot;/sys/class/uio/uio0/device/config&quot;, O_RDWR);
+        if (uiofd &lt; 0) {
+                perror(&quot;config open:&quot;);
+                return errno;
+        }
+
+        /* Read and cache command value */
+        err = pread(configfd, &amp;command_high, 1, 5);
+        if (err != 1) {
+                perror(&quot;command config read:&quot;);
+                return errno;
+        }
+        command_high &amp;= ~0x4;
+
+        for(i = 0;; ++i) {
+                /* Print out a message, for debugging. */
+                if (i == 0)
+                        fprintf(stderr, &quot;Started uio test driver.\n&quot;);
+                else
+                        fprintf(stderr, &quot;Interrupts: %d\n&quot;, icount);
+
+                /****************************************/
+                /* Here we got an interrupt from the
+                   device. Do something to it. */
+                /****************************************/
+
+                /* Re-enable interrupts. */
+                err = pwrite(configfd, &amp;command_high, 1, 5);
+                if (err != 1) {
+                        perror(&quot;config write:&quot;);
+                        break;
+                }
+
+                /* Wait for next interrupt. */
+                err = read(uiofd, &amp;icount, 4);
+                if (err != 4) {
+                        perror(&quot;uio read:&quot;);
+                        break;
+                }
+
+        }
+        return errno;
+}
+
+</programlisting>
+        </para>
+</sect1>
+
+</chapter>
+
 <appendix id="app1">
 <title>Further information</title>
 <itemizedlist>
diff --git a/MAINTAINERS b/MAINTAINERS
index 837b5985ac40..01193a4fe30e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2218,6 +2218,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git
 S:      Maintained
 F:      include/asm-generic
 
+GENERIC UIO DRIVER FOR PCI DEVICES
+M:      Michael S. Tsirkin <mst@redhat.com>
+L:      kvm@vger.kernel.org
+L:      linux-kernel@vger.kernel.org
+S:      Supported
+F:      drivers/uio/uio_pci_generic.c
+
 GFS2 FILE SYSTEM
 M:      Steven Whitehouse <swhiteho@redhat.com>
 L:      cluster-devel@redhat.com
diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
index 45200fd68534..8aa1955f35ed 100644
--- a/drivers/uio/Kconfig
+++ b/drivers/uio/Kconfig
@@ -84,4 +84,14 @@ config UIO_SERCOS3
 
           If you compile this as a module, it will be called uio_sercos3.
 
+config UIO_PCI_GENERIC
+        tristate "Generic driver for PCI 2.3 and PCI Express cards"
+        depends on PCI
+        default n
+        help
+          Generic driver that you can bind, dynamically, to any
+          PCI 2.3 compliant and PCI Express card. It is useful,
+          primarily, for virtualization scenarios.
+          If you compile this as a module, it will be called uio_pci_generic.
+
 endif
diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
index 5c2586d75797..73b2e7516729 100644
--- a/drivers/uio/Makefile
+++ b/drivers/uio/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_UIO_PDRV_GENIRQ)	+= uio_pdrv_genirq.o
 obj-$(CONFIG_UIO_SMX)   += uio_smx.o
 obj-$(CONFIG_UIO_AEC)   += uio_aec.o
 obj-$(CONFIG_UIO_SERCOS3)       += uio_sercos3.o
+obj-$(CONFIG_UIO_PCI_GENERIC)   += uio_pci_generic.o
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);
diff --git a/include/linux/pci_regs.h b/include/linux/pci_regs.h
index fcaee42c7ac2..dd0bed4f1cf0 100644
--- a/include/linux/pci_regs.h
+++ b/include/linux/pci_regs.h
@@ -42,6 +42,7 @@
 #define  PCI_COMMAND_INTX_DISABLE 0x400 /* INTx Emulation Disable */
 
 #define PCI_STATUS              0x06    /* 16 bits */
+#define  PCI_STATUS_INTERRUPT   0x08    /* Interrupt status */
 #define  PCI_STATUS_CAP_LIST    0x10    /* Support Capability List */
 #define  PCI_STATUS_66MHZ       0x20    /* Support 66 Mhz PCI 2.1 bus */
 #define  PCI_STATUS_UDF         0x40    /* Support User Definable Features [obsolete] */