linux-kernel - Re: [PATCH] eeepc-laptop: enable camera by default

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Message-ID: <4A2931F5.1090709@tuffmail.co.uk>
Date:	Fri, 05 Jun 2009 15:55:49 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	Corentin Chary <corentin.chary@...il.com>,
	acpi4asus-user@...ts.sourceforge.net, len.brown@...el.com,
	linux-kernel@...r.kernel.org, USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] eeepc-laptop: enable camera by default

Pekka Enberg wrote:
> Hi Alan,
>
> On Fri, 2009-06-05 at 15:38 +0100, Alan Jenkins wrote:
>   
>> Ok.  I didn't bother shutting down my system, but I get a similar
>> difference; 16 wakeups/s disabled v.s. 25 enabled.  Anecdotally,
>> disabling the camera does help battery life, and presumably Asus had
>> good reason to implement it!  (The shipped OS "fixes" the usability
>> problem by patching the camera apps).
>>
>> BUT I found that autosuspend didn't seem to break anything, and
>> enabling it also got me down to 16 wakeups/s.  I think this is ideal
>> because autosuspend is automatic so I can save power without manual
>> toggling.
>>
>> Here's some magic to enable autosuspend:
>>
>> # echo -n auto > /sys/bus/usb/drivers/uvcvideo/*:*/../power/level
>>
>> Ideally this wants to be enabled automatically using a udev rule.
>>     
>
> Can the kernel do this by default for this specific driver on eeepc?
>
> 			Pekka
>
>   

Auto-suspend white-listing would be done on the basis of USB ids 
(vendor, product).  At the moment it's expected that userspace should 
take ownership of it.  There's no infrastructure for in-kernel 
whitelisting.  I think.

Large lists in udev rules can work, there are already lists of USB 
devices to set permissions for libusb access, e.g. for libmtp.

[CC usb list - in the hope someone will point out if I got this wrong :-)]

Alan
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