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authorAntonios Motakis <a.motakis@virtualopensystems.com>2015-01-06 11:15:11 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-02-10 10:23:15 +0000
commit3cf385713460eb2bb4cb7ceb8ed89833b00b594b (patch)
treeb9c51c20e360b31aa2a567d3857b3039d6e08fdf /Documentation
parent8684014d71e259f62f7dc24a20324e232806b2ef (diff)
ARM: 8256/1: driver coamba: add device binding path 'driver_override'
As already demonstrated with PCI [1] and the platform bus [2], a driver_override property in sysfs can be used to bypass the id matching of a device to a AMBA driver. This can be used by VFIO to bind to any AMBA device requested by the user. [1] http://lists-archives.com/linux-kernel/28030441-pci-introduce-new-device-binding-path-using-pci_dev-driver_override.html [2] https://www.redhat.com/archives/libvir-list/2014-April/msg00382.html Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com> Reviewed-by: Kim Phillips <kim.phillips@freescale.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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+What: /sys/bus/amba/devices/.../driver_override
+Date: September 2014
+Contact: Antonios Motakis <a.motakis@virtualopensystems.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-amba > 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.