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linux/Documentation/ABI/testing/sysfs-bus-usb
Rajat Jain 70f400d4d9 driver core: Move the "removable" attribute from USB to core 
Move the "removable" attribute from USB to core in order to allow it to be
supported by other subsystem / buses. Individual buses that want to support
this attribute can populate the removable property of the device while
enumerating it with the 3 possible values -
 - "unknown"
 - "fixed"
 - "removable"
Leaving the field unchanged (i.e. "not supported") would mean that the
attribute would not show up in sysfs for that device. The UAPI (location,
symantics etc) for the attribute remains unchanged.

Move the "removable" attribute from USB to the device core so it can be
used by other subsystems / buses.

By default, devices do not have a "removable" attribute in sysfs.

If a subsystem or bus driver wants to support a "removable" attribute, it
should call device_set_removable() before calling device_register() or
device_add(), e.g.:

    device_set_removable(dev, DEVICE_REMOVABLE);
    device_register(dev);

The possible values and the resulting sysfs attribute contents are:

    DEVICE_REMOVABLE_UNKNOWN  ->  "unknown"
    DEVICE_REMOVABLE          ->  "removable"
    DEVICE_FIXED              ->  "fixed"

Convert the USB "removable" attribute to use this new device core
functionality.  There should be no user-visible change in the location or
semantics of attribute for USB devices.

Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rajat Jain <rajatja@google.com>
Link: https://lore.kernel.org/r/20210524171812.18095-1-rajatja@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-27 09:36:31 +02:00

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What: /sys/bus/usb/devices/INTERFACE/authorized
Date: August 2015
Description:
This allows to authorize (1) or deauthorize (0)
individual interfaces instead a whole device
in contrast to the device authorization.
If a deauthorized interface will be authorized
so the driver probing must be triggered manually
by writing INTERFACE to /sys/bus/usb/drivers_probe
This allows to avoid side-effects with drivers
that need multiple interfaces.
A deauthorized interface cannot be probed or claimed.
What: /sys/bus/usb/devices/usbX/interface_authorized_default
Date: August 2015
Description:
This is used as value that determines if interfaces
would be authorized by default.
The value can be 1 or 0. It's by default 1.
What: /sys/bus/usb/device/.../authorized
Date: July 2008
KernelVersion: 2.6.26
Contact: David Vrabel <david.vrabel@csr.com>
Description:
Authorized devices are available for use by device
drivers, non-authorized one are not. By default, wired
USB devices are authorized.
Certified Wireless USB devices are not authorized
initially and should be (by writing 1) after the
device has been authenticated.
What: /sys/bus/usb/device/.../wusb_cdid
Date: July 2008
KernelVersion: 2.6.27
Contact: David Vrabel <david.vrabel@csr.com>
Description:
For Certified Wireless USB devices only.
A devices's CDID, as 16 space-separated hex octets.
What: /sys/bus/usb/device/.../wusb_ck
Date: July 2008
KernelVersion: 2.6.27
Contact: David Vrabel <david.vrabel@csr.com>
Description:
For Certified Wireless USB devices only.
Write the device's connection key (CK) to start the
authentication of the device. The CK is 16
space-separated hex octets.
What: /sys/bus/usb/device/.../wusb_disconnect
Date: July 2008
KernelVersion: 2.6.27
Contact: David Vrabel <david.vrabel@csr.com>
Description:
For Certified Wireless USB devices only.
Write a 1 to force the device to disconnect
(equivalent to unplugging a wired USB device).
What: /sys/bus/usb/drivers/.../new_id
Date: October 2011
Contact: linux-usb@vger.kernel.org
Description:
Writing a device ID to this file will attempt to
dynamically add a new device ID to a USB device driver.
This may allow the driver to support more hardware than
was included in the driver's static device ID support
table at compile time. The format for the device ID is:
idVendor idProduct bInterfaceClass RefIdVendor RefIdProduct
The vendor ID and device ID fields are required, the
rest is optional. The `Ref*` tuple can be used to tell the
driver to use the same driver_data for the new device as
it is used for the reference device.
Upon successfully adding an ID, the driver will probe
for the device and attempt to bind to it. For example::
# echo "8086 10f5" > /sys/bus/usb/drivers/foo/new_id
Here add a new device (0458:7045) using driver_data from
an already supported device (0458:704c)::
# echo "0458 7045 0 0458 704c" > /sys/bus/usb/drivers/foo/new_id
Reading from this file will list all dynamically added
device IDs in the same format, with one entry per
line. For example::
# cat /sys/bus/usb/drivers/foo/new_id
8086 10f5
dead beef 06
f00d cafe
The list will be truncated at PAGE_SIZE bytes due to
sysfs restrictions.
What: /sys/bus/usb-serial/drivers/.../new_id
Date: October 2011
Contact: linux-usb@vger.kernel.org
Description:
For serial USB drivers, this attribute appears under the
extra bus folder "usb-serial" in sysfs; apart from that
difference, all descriptions from the entry
"/sys/bus/usb/drivers/.../new_id" apply.
What: /sys/bus/usb/drivers/.../remove_id
Date: November 2009
Contact: CHENG Renquan <rqcheng@smu.edu.sg>
Description:
Writing a device ID to this file will remove an ID
that was dynamically added via the new_id sysfs entry.
The format for the device ID is:
idVendor idProduct. After successfully
removing an ID, the driver will no longer support the
device. This is useful to ensure auto probing won't
match the driver to the device. For example:
# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id
Reading from this file will list the dynamically added
device IDs, exactly like reading from the entry
"/sys/bus/usb/drivers/.../new_id"
What: /sys/bus/usb/devices/.../power/usb2_hardware_lpm
Date: September 2011
Contact: Andiry Xu <andiry.xu@amd.com>
Description:
If CONFIG_PM is set and a USB 2.0 lpm-capable device is plugged
in to a xHCI host which support link PM, it will perform a LPM
test; if the test is passed and host supports USB2 hardware LPM
(xHCI 1.0 feature), USB2 hardware LPM will be enabled for the
device and the USB device directory will contain a file named
power/usb2_hardware_lpm. The file holds a string value (enable
or disable) indicating whether or not USB2 hardware LPM is
enabled for the device. Developer can write y/Y/1 or n/N/0 to
the file to enable/disable the feature.
What: /sys/bus/usb/devices/.../power/usb3_hardware_lpm_u1
/sys/bus/usb/devices/.../power/usb3_hardware_lpm_u2
Date: November 2015
Contact: Kevin Strasser <kevin.strasser@linux.intel.com>
Lu Baolu <baolu.lu@linux.intel.com>
Description:
If CONFIG_PM is set and a USB 3.0 lpm-capable device is plugged
in to a xHCI host which supports link PM, it will check if U1
and U2 exit latencies have been set in the BOS descriptor; if
the check is passed and the host supports USB3 hardware LPM,
USB3 hardware LPM will be enabled for the device and the USB
device directory will contain two files named
power/usb3_hardware_lpm_u1 and power/usb3_hardware_lpm_u2. These
files hold a string value (enable or disable) indicating whether
or not USB3 hardware LPM U1 or U2 is enabled for the device.
What: /sys/bus/usb/devices/.../ltm_capable
Date: July 2012
Contact: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Description:
USB 3.0 devices may optionally support Latency Tolerance
Messaging (LTM). They indicate their support by setting a bit
in the bmAttributes field of their SuperSpeed BOS descriptors.
If that bit is set for the device, ltm_capable will read "yes".
If the device doesn't support LTM, the file will read "no".
The file will be present for all speeds of USB devices, and will
always read "no" for USB 1.1 and USB 2.0 devices.
What: /sys/bus/usb/devices/.../(hub interface)/portX
Date: August 2012
Contact: Lan Tianyu <tianyu.lan@intel.com>
Description:
The /sys/bus/usb/devices/.../(hub interface)/portX
is usb port device's sysfs directory.
What: /sys/bus/usb/devices/.../(hub interface)/portX/connect_type
Date: January 2013
Contact: Lan Tianyu <tianyu.lan@intel.com>
Description:
Some platforms provide usb port connect types through ACPI.
This attribute is to expose these information to user space.
The file will read "hotplug", "hardwired" and "not used" if the
information is available, and "unknown" otherwise.
What: /sys/bus/usb/devices/.../(hub interface)/portX/location
Date: October 2018
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Some platforms provide usb port physical location through
firmware. This is used by the kernel to pair up logical ports
mapping to the same physical connector. The attribute exposes the
raw location value as a hex integer.
What: /sys/bus/usb/devices/.../(hub interface)/portX/quirks
Date: May 2018
Contact: Nicolas Boichat <drinkcat@chromium.org>
Description:
In some cases, we care about time-to-active for devices
connected on a specific port (e.g. non-standard USB port like
pogo pins), where the device to be connected is known in
advance, and behaves well according to the specification.
This attribute is a bit-field that controls the behavior of
a specific port:
- Bit 0 of this field selects the "old" enumeration scheme,
as it is considerably faster (it only causes one USB reset
instead of 2).
The old enumeration scheme can also be selected globally
using /sys/module/usbcore/parameters/old_scheme_first, but
it is often not desirable as the new scheme was introduced to
increase compatibility with more devices.
- Bit 1 reduces TRSTRCY to the 10 ms that are required by the
USB 2.0 specification, instead of the 50 ms that are normally
used to help make enumeration work better on some high speed
devices.
What: /sys/bus/usb/devices/.../(hub interface)/portX/over_current_count
Date: February 2018
Contact: Richard Leitner <richard.leitner@skidata.com>
Description:
Most hubs are able to detect over-current situations on their
ports and report them to the kernel. This attribute is to expose
the number of over-current situation occurred on a specific port
to user space. This file will contain an unsigned 32 bit value
which wraps to 0 after its maximum is reached. This file supports
poll() for monitoring changes to this value in user space.
Any time this value changes the corresponding hub device will send a
udev event with the following attributes::
OVER_CURRENT_PORT=/sys/bus/usb/devices/.../(hub interface)/portX
OVER_CURRENT_COUNT=[current value of this sysfs attribute]
What: /sys/bus/usb/devices/.../(hub interface)/portX/usb3_lpm_permit
Date: November 2015
Contact: Lu Baolu <baolu.lu@linux.intel.com>
Description:
Some USB3.0 devices are not friendly to USB3 LPM. usb3_lpm_permit
attribute allows enabling/disabling usb3 lpm of a port. It takes
effect both before and after a usb device is enumerated. Supported
values are "0" if both u1 and u2 are NOT permitted, "u1" if only u1
is permitted, "u2" if only u2 is permitted, "u1_u2" if both u1 and
u2 are permitted.
What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
USB 2.0 devices may support hardware link power management (LPM)
L1 sleep state. The usb2_lpm_l1_timeout attribute allows
tuning the timeout for L1 inactivity timer (LPM timer), e.g.
needed inactivity time before host requests the device to go to L1 sleep.
Useful for power management tuning.
Supported values are 0 - 65535 microseconds.
What: /sys/bus/usb/devices/.../power/usb2_lpm_besl
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
USB 2.0 devices that support hardware link power management (LPM)
L1 sleep state now use a best effort service latency value (BESL) to
indicate the best effort to resumption of service to the device after the
initiation of the resume event.
If the device does not have a preferred besl value then the host can select
one instead. This usb2_lpm_besl attribute allows to tune the host selected besl
value in order to tune power saving and service latency.
Supported values are 0 - 15.
More information on how besl values map to microseconds can be found in
USB 2.0 ECN Errata for Link Power Management, section 4.10)
What: /sys/bus/usb/devices/.../rx_lanes
Date: March 2018
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
Number of rx lanes the device is using.
USB 3.2 adds Dual-lane support, 2 rx and 2 tx lanes over Type-C.
Inter-Chip SSIC devices support asymmetric lanes up to 4 lanes per
direction. Devices before USB 3.2 are single lane (rx_lanes = 1)
What: /sys/bus/usb/devices/.../tx_lanes
Date: March 2018
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
Number of tx lanes the device is using.
USB 3.2 adds Dual-lane support, 2 rx and 2 tx -lanes over Type-C.
Inter-Chip SSIC devices support asymmetric lanes up to 4 lanes per
direction. Devices before USB 3.2 are single lane (tx_lanes = 1)
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