From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: USB disconnect/connect messages Date: Mon, 21 Jul 2003 17:25:46 +0200 Sender: alsa-devel-admin@lists.sourceforge.net Message-ID: References: <3F1B2870.3070505@superbug.demon.co.uk> Mime-Version: 1.0 (generated by SEMI 1.14.4 - "Hosorogi") Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <3F1B2870.3070505@superbug.demon.co.uk> Errors-To: alsa-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: James Courtier-Dutton Cc: alsa-devel@lists.sourceforge.net List-Id: alsa-devel@alsa-project.org At Mon, 21 Jul 2003 00:40:32 +0100, James Courtier-Dutton wrote: > > Hi, > > Is there any way to tell if a USB sound card has been disconnected or not? IIRC, this is not notified to the application. the app simply would get an error at the further access. it sounds not bad to notify the status change to the application by some way. perhaps we can add a new control element for this purpose. and after disconnection, only this element survives to communicate with the application... > I would like my application to play sound to a usb sound card, and if > the usb cable is unplugged, the application pauses, and if the usb cable > is plugged in again, the application continues. > > Example: - > Some in car stereo systems have usb ports. > I could plug a PC into the usb port, and play sound from the PC to the > car speaker system. If the driver switches off the car stereo (e.g. > Receives a mobile phone call) I want the PC to pause playback, but when > the car stereo switches on again, I want the PC to continue playback. > The car stereo switching off looks to the PC as though the usb cable has > been unplugged. from the driver side, i see it's difficult to "resume" from the disconnection to the disconnection state. you won't get the same usb_device record after re-plugging. of course, it would be possible to handle this in the application side (or possibly in alsa-lib) "as if" it's reconnected, though. Takashi ------------------------------------------------------- This SF.net email is sponsored by: VM Ware With VMware you can run multiple operating systems on a single machine. WITHOUT REBOOTING! Mix Linux / Windows / Novell virtual machines at the same time. Free trial click here: http://www.vmware.com/wl/offer/345/0