Commit 3d713e0e authored by Kim Phillips's avatar Kim Phillips Committed by Greg Kroah-Hartman
Browse files

driver core: platform: add device binding path 'driver_override' 



Needed by platform device drivers, such as the upcoming
vfio-platform driver, 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", which is an interface enhancement
for more deterministic PCI device binding, e.g., when in the
presence of hotplug.

Reviewed-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Reviewed-by: default avatarAlexander Graf <agraf@suse.de>
Reviewed-by: default avatarStuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: default avatarKim Phillips <kim.phillips@freescale.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1cec24c5

Documentation/ABI/testing/sysfs-bus-platform

0 → 100644
+20 −0
Original line number Diff line number Diff line 
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 is specified by writing a string

		to the driver_override file (echo vfio-platform > \

		driver_override) and may be cleared with an empty string

		(echo > driver_override).  This returns 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.  If no

		driver with a matching name is currently loaded in the kernel,

		the device will not bind to any driver.  This also allows

		devices to opt-out of driver binding using a driver_override

		name such as "none".  Only a single driver may be specified in

		the override, there is no support for parsing delimiters.

drivers/base/platform.c

+47 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/pm_runtime.h>

#include <linux/idr.h>

#include <linux/acpi.h>

#include <linux/limits.h>



#include "base.h"

#include "power/power.h"
@@ -191,6 +192,7 @@ static void platform_device_release(struct device *dev) 
	kfree(pa->pdev.dev.platform_data);

	kfree(pa->pdev.mfd_cell);

	kfree(pa->pdev.resource);

	kfree(pa->pdev.driver_override);

	kfree(pa);

}
@@ -698,8 +700,49 @@ 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, *cp;



	if (count > PATH_MAX)

		return -EINVAL;



	driver_override = kstrndup(buf, count, GFP_KERNEL);

	if (!driver_override)

		return -ENOMEM;



	cp = strchr(driver_override, '\n');

	if (cp)

		*cp = '\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);
@@ -755,6 +798,10 @@ 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;

include/linux/platform_device.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

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