diff options
| author | Roy Luo <royluo@google.com> | 2023-06-08 04:59:12 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-06-13 12:58:26 +0300 |
| commit | 83cb2604f641cecadc275ca18adbba4bf262320f (patch) | |
| tree | 1cae3704f2f1385b02827ab2721f30c2c08d5776 /Documentation/ABI | |
| parent | edd60d24bd858cef165274e4cd6cab43bdc58d15 (diff) | |
| download | linux-83cb2604f641cecadc275ca18adbba4bf262320f.tar.xz | |
usb: core: add sysfs entry for usb device state
Expose usb device state to userland as the information is useful in
detecting non-compliant setups and diagnosing enumeration failures.
For example:
- End-to-end signal integrity issues: the device would fail port reset
repeatedly and thus be stuck in POWERED state.
- Charge-only cables (missing D+/D- lines): the device would never enter
POWERED state as the HC would not see any pullup.
What's the status quo?
We do have error logs such as "Cannot enable. Maybe the USB cable is bad?"
to flag potential setup issues, but there's no good way to expose them to
userspace.
Why add a sysfs entry in struct usb_port instead of struct usb_device?
The struct usb_device is not device_add() to the system until it's in
ADDRESS state hence we would miss the first two states. The struct
usb_port is a better place to keep the information because its life
cycle is longer than the struct usb_device that is attached to the port.
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202306042228.e532af6e-oliver.sang@intel.com
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Roy Luo <royluo@google.com>
Message-ID: <20230608015913.1679984-1-royluo@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-usb | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index cb172db41b34..be663258b9b7 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -292,6 +292,16 @@ Description: which is marked with early_stop has failed to initialize, it will ignore all future connections until this attribute is clear. +What: /sys/bus/usb/devices/.../<hub_interface>/port<X>/state +Date: June 2023 +Contact: Roy Luo <royluo@google.com> +Description: + Indicates current state of the USB device attached to the port. + Valid states are: 'not-attached', 'attached', 'powered', + 'reconnecting', 'unauthenticated', 'default', 'addressed', + 'configured', and 'suspended'. This file supports poll() to + monitor the state change from user space. + What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout Date: May 2013 Contact: Mathias Nyman <mathias.nyman@linux.intel.com> |