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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
782a985d7a ("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>
59 lines
2.6 KiB
Plaintext
59 lines
2.6 KiB
Plaintext
What: /sys/bus/css/devices/.../type
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Date: March 2008
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Contact: Cornelia Huck <cornelia.huck@de.ibm.com>
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linux-s390@vger.kernel.org
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Description: Contains the subchannel type, as reported by the hardware.
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This attribute is present for all subchannel types.
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What: /sys/bus/css/devices/.../modalias
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Date: March 2008
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Contact: Cornelia Huck <cornelia.huck@de.ibm.com>
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linux-s390@vger.kernel.org
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Description: Contains the module alias as reported with uevents.
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It is of the format css:t<type> and present for all
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subchannel types.
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What: /sys/bus/css/drivers/io_subchannel/.../chpids
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Date: December 2002
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Contact: Cornelia Huck <cornelia.huck@de.ibm.com>
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linux-s390@vger.kernel.org
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Description: Contains the ids of the channel paths used by this
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subchannel, as reported by the channel subsystem
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during subchannel recognition.
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Note: This is an I/O-subchannel specific attribute.
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Users: s390-tools, HAL
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What: /sys/bus/css/drivers/io_subchannel/.../pimpampom
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Date: December 2002
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Contact: Cornelia Huck <cornelia.huck@de.ibm.com>
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linux-s390@vger.kernel.org
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Description: Contains the PIM/PAM/POM values, as reported by the
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channel subsystem when last queried by the common I/O
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layer (this implies that this attribute is not necessarily
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in sync with the values current in the channel subsystem).
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Note: This is an I/O-subchannel specific attribute.
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Users: s390-tools, HAL
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What: /sys/bus/css/devices/.../driver_override
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Date: June 2019
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Contact: Cornelia Huck <cohuck@redhat.com>
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linux-s390@vger.kernel.org
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Description: This file allows the driver for a device to be specified. When
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specified, only a driver with a name matching the value written
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to driver_override will have an opportunity to bind to the
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device. The override is specified by writing a string to the
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driver_override file (echo vfio-ccw > driver_override) and
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may be cleared with an empty string (echo > driver_override).
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This returns the device to standard matching rules binding.
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Writing to driver_override does not automatically unbind the
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device from its current driver or make any attempt to
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automatically load the specified driver. If no driver with a
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matching name is currently loaded in the kernel, the device
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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,
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there is no support for parsing delimiters.
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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.
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