Messages in this thread | | | From | Jörg-Volker Peetz <> | Subject | [BISECTED] (?) since 3.16: USB video cam of an HP Pavilion dv7 laptop not working | Date | Mon, 08 Sep 2014 17:17:05 +0200 |
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Since 3.16 the builtin USB video cam of an HP Pavilion dv7 laptop shows only a black screen with the application guvcview although the video LED is turned on. There is no hint in dmesg. Also the output of guvcview shows no conspicuousness.
With kernel version 3.15.9 the camera works.
I tried to bisect between good v3.15 and bad v3.16, which identified
commit 9262c19d14c433a6a1ba25c3ff897cb89e412309 Author: Dan Williams <dan.j.williams@intel.com> Date: Tue May 20 18:08:12 2014 -0700
usb: disable port power control if not supported in wHubCharacteristics
A hub indicates whether it supports per-port power control via the wHubCharacteristics field in its descriptor. If it is not supported a hub will still emulate ClearPortPower(PORT_POWER) requests by stopping the link state machine. However, since this does not save power do not bother suspending.
This also consolidates support checks into a hub_is_port_power_switchable() helper.
Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In the bad bisection steps the video device even was not found. Therefore, I'm not sure if I identified the right culprit.
Thanks for any help, Jörg-Volker.
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