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Date: Tue, 09 Sep 2014 13:36:02 +0200
From: Jörg-Volker Peetz <jvpeetz@....de>
To: linux-kernel@...r.kernel.org
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [BISECTED] (?) since 3.16: USB video cam of an HP Pavilion dv7
laptop not working
Jörg-Volker Peetz wrote on 09/08/2014 17:17:
> 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@...el.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@...land.harvard.edu>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> In the bad bisection steps the video device even was not found. Therefore, I'm
> not sure if I identified the right culprit.
>
As you suggested Dan, I reverted this commit on top of 3.16.0 (the commit could
not be reverted cleanly, I had to do it manually, patch appended). But still I
see a black picture from the camera. So this commit is not the culprit.
How to proceed with the bisection?
--
Regards,
Jörg-Volker.
View attachment "my-patch" of type "text/plain" (2926 bytes)
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