Patchwork [RFC] PCI: Introduce new device binding path using pci_dev.driver_override

login
register
mail settings
Submitter Kim Phillips
Date April 5, 2014, 1:35 a.m.
Message ID <20140404203512.5b5ac8a134a71065518712c3@freescale.com>
Download mbox | patch
Permalink /patch/337134/
State Superseded
Headers show

Comments

Kim Phillips - April 5, 2014, 1:35 a.m.
Needed by platform device drivers, such as the vfio-platform driver [1],
in order to bypass the existing OF, ACPI, id_table and name string matches,
and successfully be able to be bound to any device, like so:

echo vfio-platform > /sys/bus/platform/devices/fff51000.ethernet/driver_override
echo fff51000.ethernet > /sys/bus/platform/devices/fff51000.ethernet/driver/unbind
echo fff51000.ethernet > /sys/bus/platform/drivers_probe

This mimics "PCI: Introduce new device binding path using
pci_dev.driver_override" [2], which is an interface enhancement
for more deterministic PCI device binding, e.g., when in the
presence of hotplug.

[1] http://lkml.iu.edu/hypermail/linux/kernel/1402.1/00177.html
[2] http://thread.gmane.org/gmane.linux.kernel.iommu/4605

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
---
if this looks ok, should it be included in the next version of the
vfio-platform submission series, like last time ([1] above)?

 Documentation/ABI/testing/sysfs-bus-platform | 17 ++++++++++
 drivers/base/platform.c                      | 46 ++++++++++++++++++++++++++++
 include/linux/platform_device.h              |  1 +
 3 files changed, 64 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-platform
Guenter Roeck - April 5, 2014, 2:07 a.m.
On 04/04/2014 06:35 PM, Kim Phillips wrote:
> Needed by platform device drivers, such as the vfio-platform driver [1],
> in order to bypass the existing OF, ACPI, id_table and name string matches,
> and successfully be able to be bound to any device, like so:
>
> echo vfio-platform > /sys/bus/platform/devices/fff51000.ethernet/driver_override
> echo fff51000.ethernet > /sys/bus/platform/devices/fff51000.ethernet/driver/unbind
> echo fff51000.ethernet > /sys/bus/platform/drivers_probe
>
> This mimics "PCI: Introduce new device binding path using
> pci_dev.driver_override" [2], which is an interface enhancement
> for more deterministic PCI device binding, e.g., when in the
> presence of hotplug.
>
> [1] http://lkml.iu.edu/hypermail/linux/kernel/1402.1/00177.html
> [2] http://thread.gmane.org/gmane.linux.kernel.iommu/4605
>
> Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
> ---
> if this looks ok, should it be included in the next version of the
> vfio-platform submission series, like last time ([1] above)?
>
>   Documentation/ABI/testing/sysfs-bus-platform | 17 ++++++++++
>   drivers/base/platform.c                      | 46 ++++++++++++++++++++++++++++
>   include/linux/platform_device.h              |  1 +
>   3 files changed, 64 insertions(+)
>   create mode 100644 Documentation/ABI/testing/sysfs-bus-platform
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
> new file mode 100644
> index 0000000..6b14a6a
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-platform
> @@ -0,0 +1,17 @@
> +What:		/sys/bus/platform/devices/.../driver_override
> +Date:		April 2014
> +Contact:	Kim Phillips <kim.phillips@freescale.com>
> +Description:
> +		This file allows the driver for a device to be specified
> +		which will override standard OF, ACPI, ID table, and name
> +		matching.  When specified, only a driver with a name matching
> +		the value written to driver_override will have an opportunity
> +		to bind to the device.  The override may be cleared by
> +		writing an empty string (ex. echo > driver_override), returning
> +		the device to standard matching rules binding.  Writing to
> +		driver_override does not automatically unbind the device from
> +		its current driver or make any attempt to automatically load
> +		the specified driver name.  If no driver with a matching name
> +		is currently loaded in the kernel, no match will be found.
> +		This also allows devices to opt-out of driver binding using
> +		a driver_override name such as "none".
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index e714709..ded1db1 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -22,6 +22,7 @@
>   #include <linux/pm_runtime.h>
>   #include <linux/idr.h>
>   #include <linux/acpi.h>
> +#include <linux/limits.h>
>
>   #include "base.h"
>   #include "power/power.h"
> @@ -690,8 +691,49 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
>   }
>   static DEVICE_ATTR_RO(modalias);
>
> +static ssize_t driver_override_store(struct device *dev,
> +				     struct device_attribute *attr,
> +				     const char *buf, size_t count)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	char *driver_override, *old = pdev->driver_override;
> +
> +	if (count > PATH_MAX)
> +		return -EINVAL;
> +
> +	driver_override = kstrndup(buf, count, GFP_KERNEL);
> +	if (!driver_override)
> +		return -ENOMEM;
> +
> +	while (strlen(driver_override) &&
> +	       driver_override[strlen(driver_override) - 1] == '\n')
> +		driver_override[strlen(driver_override) - 1] = '\0';
> +

Seems to me that something like

	cp = strchr(driver_override, '\n');
	if (cp)
		*cp = '\0';

would be much simpler.

Guenter

--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
new file mode 100644
index 0000000..6b14a6a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-platform
@@ -0,0 +1,17 @@ 
+What:		/sys/bus/platform/devices/.../driver_override
+Date:		April 2014
+Contact:	Kim Phillips <kim.phillips@freescale.com>
+Description:
+		This file allows the driver for a device to be specified
+		which will override standard OF, ACPI, ID table, and name
+		matching.  When specified, only a driver with a name matching
+		the value written to driver_override will have an opportunity
+		to bind to the device.  The override may be cleared by
+		writing an empty string (ex. echo > driver_override), returning
+		the device to standard matching rules binding.  Writing to
+		driver_override does not automatically unbind the device from
+		its current driver or make any attempt to automatically load
+		the specified driver name.  If no driver with a matching name
+		is currently loaded in the kernel, no match will be found.
+		This also allows devices to opt-out of driver binding using
+		a driver_override name such as "none".
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index e714709..ded1db1 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -22,6 +22,7 @@ 
 #include <linux/pm_runtime.h>
 #include <linux/idr.h>
 #include <linux/acpi.h>
+#include <linux/limits.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -690,8 +691,49 @@  static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
 }
 static DEVICE_ATTR_RO(modalias);
 
+static ssize_t driver_override_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	char *driver_override, *old = pdev->driver_override;
+
+	if (count > PATH_MAX)
+		return -EINVAL;
+
+	driver_override = kstrndup(buf, count, GFP_KERNEL);
+	if (!driver_override)
+		return -ENOMEM;
+
+	while (strlen(driver_override) &&
+	       driver_override[strlen(driver_override) - 1] == '\n')
+		driver_override[strlen(driver_override) - 1] = '\0';
+
+	if (strlen(driver_override)) {
+		pdev->driver_override = driver_override;
+	} else {
+		kfree(driver_override);
+		pdev->driver_override = NULL;
+	}
+
+	kfree(old);
+
+	return count;
+}
+
+static ssize_t driver_override_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+
+	return sprintf(buf, "%s\n", pdev->driver_override);
+}
+static DEVICE_ATTR_RW(driver_override);
+
+
 static struct attribute *platform_dev_attrs[] = {
 	&dev_attr_modalias.attr,
+	&dev_attr_driver_override.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(platform_dev);
@@ -747,6 +789,10 @@  static int platform_match(struct device *dev, struct device_driver *drv)
 	struct platform_device *pdev = to_platform_device(dev);
 	struct platform_driver *pdrv = to_platform_driver(drv);
 
+	/* When driver_override is set, only bind to the matching driver */
+	if (pdev->driver_override)
+		return !strcmp(pdev->driver_override, drv->name);
+
 	/* Attempt an OF style match first */
 	if (of_driver_match_device(dev, drv))
 		return 1;
diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
index 16f6654..153d303 100644
--- a/include/linux/platform_device.h
+++ b/include/linux/platform_device.h
@@ -28,6 +28,7 @@  struct platform_device {
 	struct resource	*resource;
 
 	const struct platform_device_id	*id_entry;
+	char *driver_override; /* Driver name to force a match */
 
 	/* MFD cell pointer */
 	struct mfd_cell *mfd_cell;