From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: USB sound auto-suspend not working Date: Wed, 18 Dec 2013 09:51:46 +0100 Message-ID: <1387356706.1554.1.camel@linux-fkkt.site> References: <20131217225548.GA3029@xanatos> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131217225548.GA3029@xanatos> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sarah Sharp Cc: Takashi Iwai , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jaroslav Kysela , alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org List-Id: alsa-devel@alsa-project.org On Tue, 2013-12-17 at 14:55 -0800, Sarah Sharp wrote: > Hi Oliver and Takashi, > > I've noticed that in the last couple kernel releases or so, I can't get > USB webcams to suspend. It turns out that the USB sound interface is > keeping the device active, even when the device is not playing sound. > This goes back as far as 3.10, but I haven't tried older kernels. This > is testing on Ubuntu 13.10. > > Commit 88a8516a2128a6d078a106ead48092240e8a138f "ALSA: usbaudio: > implement USB autosuspend" went into kernel 2.6.39. The commit message > says the device is prevented from suspending if the pcm or midi channel > files are open. > > I plugged in a USB speaker, and ran lsof to see which files were open > (output is attached). AFAICT, only the USB sound device's control files > are open, and I don't have any midi files. Is that sensible? In case of a webcam the problem is input, not output. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html