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

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Date:	Thu, 25 Apr 2013 14:33:06 +0800
From:	Adam Lee <adam.lee@...onical.com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	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"

On Wed, Apr 24, 2013 at 11:17:52AM +0200, Laurent Pinchart wrote:
> Hi Adam,
> 
> Thanks for the patch.
> 
> On Wednesday 24 April 2013 15:57:19 adam.lee@...onical.com wrote:
> > From: Adam Lee <adam.lee@...onical.com>
> > 
> > This reverts commit 3dae8b41dc5651f8eb22cf310e8b116480ba25b7.
> > 
> > 1, I do have a Chicony webcam, implements autosuspend in a broken way,
> > make `poweroff` performs rebooting when its autosuspend enabled.
> > 
> > 2, There are other webcams which don't support autosuspend too, like
> > https://patchwork.kernel.org/patch/2356141/
> > 
> > 3, kernel removed USB_QUIRK_NO_AUTOSUSPEND in
> > a691efa9888e71232dfb4088fb8a8304ffc7b0f9, because autosuspend is
> > disabled by default.
> > 
> > So, we need to disable autosuspend in uvcvideo, maintaining a quirk list
> > only for uvcvideo is not a good idea.
> 
> I've received very few bug reports about broken auto-suspend support in UVC 
> devices. Most of them could be solved by setting the RESET_RESUME quirk in USB 
> core, only the Creative Live! Cam Optia AF required a quirk in the uvcvideo 
> driver. I would thus rather use the available quirks (USB_QUIRK_RESET_RESUME 
> if possible, UVC_QUIRK_DISABLE_AUTOSUSPEND otherwise) than killing power 
> management for the vast majority of webcams that behave correctly.

Here comes another one, integrated Chicony webcam 04f2:b39f, its
autosuspend makes `poweroff` performs rebooting at the laptop I'm
working on. I tried USB_QUIRK_RESET_RESUME, not helping.

The quirks list will go longer and longer absolutely, do uvcvideo wanna
maintain that? And why only uvcvideo do this in kernel space which
against general USB module?

I still suggest we disable it by default, people can enable it in udev
just like almost all distroes do for udisks. Please consider about it.

-- 
Regards,
Adam Lee
Hardware Enablement
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