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Message-ID: <20090716170346.GA22095@redhat.com>
Date: Thu, 16 Jul 2009 20:03:46 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Greg KH <gregkh@...e.de>
Cc: "Hans J. Koch" <hjk@...utronix.de>, anthony@...emonkey.ws,
avi@...hat.com, kvm@...r.kernel.org, chrisw@...hat.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4] uio: add generic driver for PCI 2.3 devices
On Thu, Jul 16, 2009 at 08:52:08AM -0700, Greg KH wrote:
> On Thu, Jul 16, 2009 at 05:12:55PM +0200, Hans J. Koch wrote:
> > On Thu, Jul 16, 2009 at 05:07:10PM +0300, Michael S. Tsirkin wrote:
> > > On Wed, Jul 15, 2009 at 03:08:29PM -0700, Greg KH wrote:
> > > > How about moving that documentation into a place that people will notice
> > > > it, like the rest of the UIO documentation?
> > >
> > > Greg,
> > >
> > > would it make more sense to add this to
> > > Documentation/DocBook/uio-howto.xml, or to create
> > > Documentation/uio_pci_generic.txt ?
> >
> > Hi Michael,
> > I'd prefer to have it in uio-howto.xml so that people only have to look in
> > one place. In does not have to be very detailled, just a short explanation
> > what this driver is all about and a short example how to use it.
>
> I agree, that would be the best place for it.
>
> thanks,
>
> greg k-h
OK. Could you take a look at the following please?
-->
doc: Document uio_pci_generic
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl
index 8f6e3b2..4d4ce0e 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@...hat.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 "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>
--
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