linux-kernel - Re: [PATCH] Revert "V4L/DVB: uvc: Enable USB autosuspend by default on uvcvideo"

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Message-ID: <2929853.aH7hYkoiDo@avalon>
Date:	Mon, 30 Sep 2013 16:49:10 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	VDR User <user.vdr@...il.com>
Cc:	Adam Lee <adam.lee@...onical.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg@...hat.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	"open list:USB VIDEO CLASS" <linux-media@...r.kernel.org>
Subject: Re: [PATCH] Revert "V4L/DVB: uvc: Enable USB autosuspend by default on uvcvideo"

Hi,

On Tuesday 24 September 2013 08:55:19 VDR User wrote:
> On Tue, Sep 24, 2013 at 4:34 AM, Laurent Pinchart wrote:
> > I've discussed this issue during LPC last week, and I still believe we
> > should enable auto-suspend. The feature really saves power, without it my
> > C910 Logitech webcam gets hot even when unused.
> > 
> > If we disable auto-suspend by default and enable it from userspace only a
> > handful of devices will get auto-suspended. Unless we can get distros to
> > automatically test auto-suspend on unknown webcam models and report the
> > results to update a central data base (which would grow much bigger than a
> > quirks list in the driver in my opinion), disabling auto-suspend would be
> > a serious regression.
> 
> Setting defaults which knowingly cause problems is a horrible idea. Just
> because it works for you and your setup is no justification to force it upon
> everyone. This is certainly a feature that, if wanted, can be enabled by the
> user.

It's not just my setup, auto-suspend works for the vast majority of webcams. 
It has been enabled three years ago, with a report that Fedora had enabled it 
by carrying a kernel patch for a while, without any user complaint.

> I don't see any reasonable argument against letting the user enable it if
> he/she wants it.

USB autosuspend is an important power saving feature. I would be fine with 
enabling it in userspace if we could find a reasonable, cross-distro way to 
create, maintain and distribute the list of devices that support USB 
autosuspend properly.

-- 
Regards,

Laurent Pinchart

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