hc
2023-12-11 d2ccde1c8e90d38cee87a1b0309ad2827f3fd30d
kernel/Documentation/ABI/testing/sysfs-bus-css
....@@ -20,6 +20,7 @@
2020 Description: Contains the ids of the channel paths used by this
2121 subchannel, as reported by the channel subsystem
2222 during subchannel recognition.
23
+
2324 Note: This is an I/O-subchannel specific attribute.
2425 Users: s390-tools, HAL
2526
....@@ -31,5 +32,30 @@
3132 channel subsystem when last queried by the common I/O
3233 layer (this implies that this attribute is not necessarily
3334 in sync with the values current in the channel subsystem).
35
+
3436 Note: This is an I/O-subchannel specific attribute.
3537 Users: s390-tools, HAL
38
+
39
+What: /sys/bus/css/devices/.../driver_override
40
+Date: June 2019
41
+Contact: Cornelia Huck <cohuck@redhat.com>
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+ linux-s390@vger.kernel.org
43
+Description: This file allows the driver for a device to be specified. When
44
+ specified, only a driver with a name matching the value written
45
+ to driver_override will have an opportunity to bind to the
46
+ device. The override is specified by writing a string to the
47
+ driver_override file (echo vfio-ccw > driver_override) and
48
+ may be cleared with an empty string (echo > driver_override).
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+ This returns the device to standard matching rules binding.
50
+ Writing to driver_override does not automatically unbind the
51
+ device from its current driver or make any attempt to
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+ automatically load the specified driver. If no driver with a
53
+ matching name is currently loaded in the kernel, the device
54
+ will not bind to any driver. This also allows devices to
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+ opt-out of driver binding using a driver_override name such as
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+ "none". Only a single driver may be specified in the override,
57
+ there is no support for parsing delimiters.
58
+
59
+ Note that unlike the mechanism of the same name for pci, this
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+ file does not allow to override basic matching rules. I.e.,
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+ the driver must still match the subchannel type of the device.