diff options
| author | Cornelia Huck <cohuck@redhat.com> | 2019-06-13 13:08:15 +0200 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2019-07-02 16:00:26 +0200 |
| commit | ebc3d179150347f3b6d97d8f249378bb2218f95e (patch) | |
| tree | fd608926e7c655a331816d91722b45ef4cec11e5 /Documentation/ABI | |
| parent | dbd66558dd28e69471cac7c1431bb0d8df221498 (diff) | |
s390/cio: introduce driver_override on the css bus
Sometimes, we want to control which of the matching drivers
binds to a subchannel device (e.g. for subchannels we want to
handle via vfio-ccw).
For pci devices, a mechanism to do so has been introduced in
782a985d7af2 ("PCI: Introduce new device binding path using
pci_dev.driver_override"). It makes sense to introduce the
driver_override attribute for subchannel devices as well, so
that we can easily extend the 'driverctl' tool (which makes
use of the driver_override attribute for pci).
Note that unlike pci we still require a driver override to
match the subchannel type; matching more than one subchannel
type is probably not useful anyway.
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-css | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-css b/Documentation/ABI/testing/sysfs-bus-css index 2979c40c10e9..966f8504bd7b 100644 --- a/Documentation/ABI/testing/sysfs-bus-css +++ b/Documentation/ABI/testing/sysfs-bus-css @@ -33,3 +33,26 @@ Description: Contains the PIM/PAM/POM values, as reported by the in sync with the values current in the channel subsystem). Note: This is an I/O-subchannel specific attribute. Users: s390-tools, HAL + +What: /sys/bus/css/devices/.../driver_override +Date: June 2019 +Contact: Cornelia Huck <cohuck@redhat.com> + linux-s390@vger.kernel.org +Description: This file allows the driver for a device to be specified. 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-ccw > 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. + Note that unlike the mechanism of the same name for pci, this + file does not allow to override basic matching rules. I.e., + the driver must still match the subchannel type of the device. |