diff options
| author | Nicolas Boichat <drinkcat@chromium.org> | 2018-05-28 14:32:18 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-31 12:48:17 +0200 |
| commit | 25244227158e1502062041365a439a54cb8fe673 (patch) | |
| tree | 87af664545c88bc045cd1598c79caad305d77178 /Documentation/ABI | |
| parent | 380375b937211376f1dba4543460a14d3df9f04d (diff) | |
| download | linux-25244227158e1502062041365a439a54cb8fe673.tar.bz2 | |
usb: hub: Per-port setting to use old enumeration scheme
The "old" enumeration scheme is considerably faster (it takes
~244ms instead of ~356ms to get the descriptor).
It is currently only possible to use the old scheme globally
(/sys/module/usbcore/parameters/old_scheme_first), which is not
desirable as the new scheme was introduced to increase compatibility
with more devices.
However, in our case, we care about time-to-active for a specific
USB device (which we make the firmware for), on a specific port
(that is pogo-pin based: not a standard USB port). This new
sysfs option makes it possible to use the old scheme on a single
port only.
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-usb | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index c6e9b30f05b1..a31a66d62cbb 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -189,6 +189,24 @@ Description: The file will read "hotplug", "wired" and "not used" if the information is available, and "unknown" otherwise. +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. + What: /sys/bus/usb/devices/.../(hub interface)/portX/over_current_count Date: February 2018 Contact: Richard Leitner <richard.leitner@skidata.com> |