uio: add generic driver for PCI 2.3 devices

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

Changes since v1:
- some naming changes
- do a single read to get both command and status register Changes since v2:
- remove irqcontrol: user can enable interrupts by writing command register directly
- don't claim resources as we don't support mmap yet, but note the intent to do so in the commit log
Changes since v3:
- minor driver version fix

 MAINTAINERS                   |    8 ++
 drivers/uio/Kconfig           |   10 ++
 drivers/uio/Makefile          |    1 +
 drivers/uio/uio_pci_generic.c |  207 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pci_regs.h      |    1 +
 5 files changed, 227 insertions(+), 0 deletions(-)
 create mode 100644 drivers/uio/uio_pci_generic.c

MAINTAINERS +8 -0

index 18c3f0c..39c7207 100644
@@ -2538,6 +2538,14 @@ 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
+P:	Michael S. Tsirkin
+M:	[email protected]
+L:	[email protected]
+L:	[email protected]
+S:	Supported
+F:	drivers/uio/uio_pci_generic.c
+
 GFS2 FILE SYSTEM
 P:	Steven Whitehouse
 M:	[email protected]

drivers/uio/Kconfig +10 -0

index 7f86534..0f14c8e 100644
@@ -89,4 +89,14 @@ 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

drivers/uio/Makefile +1 -0

index 5c2586d..73b2e75 100644
@@ -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

drivers/uio/uio_pci_generic.c new file +207 -0

new file mode 100644
index 0000000..313da35
@@ -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 <[email protected]>
+ *
+ * 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 <[email protected]>"
+#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);

include/linux/pci_regs.h +1 -0

index fcaee42..dd0bed4 100644
@@ -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] */

Signature · 1 line

1.6.2.5

Quoted 11 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

Quoted 3 lines

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Well, I'm not enough of a PCI expert to tell whether your 2.3-test works or not (can it have side effects, e.g. trigger an interrupt when you toggle that bit?). I've added Jesse Barnes to Cc: since you modify a PCI core header file. If there are no objections from the PCI people, I guess we can take this.

Quoted 16 lines · On Wed, 15 Jul 2009 23:39:11 +0200 "Hans J. Koch" <[email protected]> wrote:

Quoted 11 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

Quoted 3 lines

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Quoted 5 lines

Well, I'm not enough of a PCI expert to tell whether your 2.3-test works or not (can it have side effects, e.g. trigger an interrupt when you toggle that bit?). I've added Jesse Barnes to Cc: since you modify a PCI core header file. If there are no objections from the PCI people, I guess we can take this.

pci_reg.h portion looks fine to me, and only supporting devices with the interrupt disable bit certainly simplifies things. There were some other questions on the thread though (like Greg's similar driver); not sure if you've answered those yet.

Signature · 1 line

Jesse Barnes, Intel Open Source Technology Center

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

Quoted 18 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Quoted 5 lines

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

How does this play with the pci-stub driver that I thought was written to solve this very problem?

Will it conflict?

In fact, it looks like you copied the comments for this driver directly from the pci-stub driver :)

How about moving that documentation into a place that people will notice it, like the rest of the UIO documentation?

And right now you are just sending the irq to userspace, what is userspace supposed to do with it?

Do you have a userspace program that
uses this interface today to verify that everything works? If so, care to provide a pointer to it?

thanks,

greg k-h

Quoted 20 lines · Greg KH

Quoted 19 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Quoted 8 lines

Quoted 5 lines

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

How does this play with the pci-stub driver that I thought was written to solve this very problem?

AFAIK the problem pci stub was written to solve is simply to bind to a device. You then have to use another kernel module which looks the device up with something like pci_get_bus_and_slot to do anything useful. In particular, for non-shared interrupts, we can disable the interrupt in the apic. But this does not work well for shared interrupts. Thus this work.

The uio driver will be used in virtualization scenarious, a couple of possible ones that have been mentioned on the kvm list are:
- device assignment (guest access to device) for simple devices with shared interrupts: emulating PCI is tricky enough to better be done in userspace. shared interrupt support is important as it happens with real devices

- simple communication between guest and host:
we create a virtual device in host, and userspace driver in guest gets events and passes them on to e.g. dbus. shared interrupt support is important to avoid wasting irqs

Quoted 1 line

Will it conflict?

No in a sense that you can't bind both drivers to the same device.

Quoted 2 lines

In fact, it looks like you copied the comments for this driver directly from the pci-stub driver :)

Right.

Quoted 2 lines

How about moving that documentation into a place that people will notice it, like the rest of the UIO documentation?

OK.

Quoted 2 lines

And right now you are just sending the irq to userspace, what is userspace supposed to do with it?

Userspace uses libpci (i.e. pci sysfs) to talk to the device and to re-enable interrupts by writing to the command register.

In the case of device assignment, this will be qemu which acts as a proxy for driver running in guest context. In case of uio loaded in guest, the driver will be in guest userspace, and the device is emulated in qemu.

Quoted 3 lines

Do you have a userspace program that
uses this interface today to verify that everything works? If so, care to provide a pointer to it?

Sure. I used an emulated device for this.
First, you patch qemu to add the device:
http://www.linux-kvm.org/downloads/mst/test_irq.patch

Now, run with the new kernel (-kernel flag), adding
-device test-irq

Once in guest, assign the device id
echo "1af4 2009" > /sys/bus/pci/drivers/uio_pci_generic/new_id

Compile and run this driver:
http://www.linux-kvm.org/downloads/mst/testuio.c
(it does not use any libraries besides libc,
so just gcc testuio.c -o testuio)

And now make the device assert interrupts, like this:

while
sleep 1
do
setpci -s 00:04.0 0x40.B=0x1
done

You should see messages printed as the driver gets interrupts, but no error messages about missed interrupts.

Quoted 3 lines

thanks,

greg k-h

--
To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html

Quoted 37 lines · On Thursday 16 July 2009 20:31:01 Michael S. Tsirkin wrote:

Quoted 20 lines · Greg KH

Quoted 19 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Quoted 8 lines

Quoted 5 lines

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

How does this play with the pci-stub driver that I thought was written to solve this very problem?

AFAIK the problem pci stub was written to solve is simply to bind to a device. You then have to use another kernel module which looks the device up with something like pci_get_bus_and_slot to do anything useful. In particular, for non-shared interrupts, we can disable the interrupt in the apic. But this does not work well for shared interrupts. Thus this work.

Quoted 6 lines

The uio driver will be used in virtualization scenarious, a couple of possible ones that have been mentioned on the kvm list are:
- device assignment (guest access to device) for simple devices with shared interrupts: emulating PCI is tricky enough to better be done in userspace. shared interrupt support is important as it happens with real devices

One comments for shared interrupt: if you means guest device shares interrupt with device in other domain(that means guest or host), it's still a security hole, and our position seems still won't-do it. Could you explain how the situation change with this patch? I am not sure if I understand your meaning completely...

Thanks.

Quoted 19 lines · Greg KH

Quoted 18 lines · Michael S. Tsirkin

This adds a generic uio driver that can bind to any PCI device. First user will be virtualization where a qemu userspace process needs to give guest OS access to the device.

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. Driver detects this support, and won't bind to devices which do not support the Interrupt Disable Bit in the command register.

It's expected that more features of interest to virtualization will be added to this driver in the future. Possibilities are: mmap for device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.

Acked-by Chris Wright <[email protected]>

Signed-off-by Michael S. Tsirkin <[email protected]>

---

Quoted 8 lines

Quoted 5 lines

Hans, Greg, please review and consider for upstream.

This is intended to solve the problem in virtualization that shared interrupts do not work with assigned devices. Earlier versions of this patch have circulated on kvm@vger.

How does this play with the pci-stub driver that I thought was written to solve this very problem?

AFAIK the problem pci stub was written to solve is simply to bind to a device. You then have to use another kernel module which looks the device up with something like pci_get_bus_and_slot to do anything useful. In particular, for non-shared interrupts, we can disable the interrupt in the apic. But this does not work well for shared interrupts. Thus this work.

The uio driver will be used in virtualization scenarious, a couple of possible ones that have been mentioned on the kvm list are:
- device assignment (guest access to device) for simple devices with shared interrupts: emulating PCI is tricky enough to better be done in userspace. shared interrupt support is important as it happens with real devices
- simple communication between guest and host:
we create a virtual device in host, and userspace
driver in guest gets events and passes them on
to e.g. dbus. shared interrupt support is important
to avoid wasting irqs

How about moving that documentation into a place that people will notice it, like the rest of the UIO documentation?

Quoted 2 lines · Greg KH

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 ?

Quoted 6 lines · Michael S. Tsirkin

Quoted 2 lines · Greg KH

How about moving that documentation into a place that people will notice it, like the rest of the UIO documentation?

Greg,

Quoted 3 lines

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.

Quoted 7 lines · Hans J. Koch

Quoted 6 lines · Michael S. Tsirkin

Quoted 2 lines · Greg KH

How about moving that documentation into a place that people will notice it, like the rest of the UIO documentation?

Greg,

Quoted 8 lines

Quoted 3 lines

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

Quoted 17 lines · Greg KH

Quoted 15 lines · Hans J. Koch

Quoted 9 lines · Michael S. Tsirkin

Quoted 2 lines · Greg KH

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.

Quoted 5 lines

I agree, that would be the best place for it.

thanks,

greg k-h

OK. Could you take a look at the following please?