From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: Some information about UsbPre2 UAC2 support Date: Sat, 26 Jan 2013 21:29:10 +0100 Message-ID: <51043C96.40508@ladisch.de> References: <199306935.463022264.1359222606997.JavaMail.root@spooler2-g27.priv.proxad.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com [66.111.4.29]) by alsa0.perex.cz (Postfix) with ESMTP id 040F6262600 for ; Sat, 26 Jan 2013 21:30:03 +0100 (CET) In-Reply-To: <199306935.463022264.1359222606997.JavaMail.root@spooler2-g27.priv.proxad.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: shal@free.fr Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org shal@free.fr wrote: > For some compatibility raison, Sound device developer want only send a UAC1 configuration when the Operating system is Windows. > The used method is based on the length of the setup packet during the device get_descriptor function. > If the length is 64, the OS is considered as Windows. > Linux have choosen also this value. Because there are buggy devices that haven been tested only with Windows and will blow up if other values are chosen. I guess somebody has to add a quirk for this device to the driver. > Now, the USB device descriptor has two configuration descriptors :the first is a UAC1 and the second is a UAC2. > > As UAC1 is a valid configuration descriptor, the usb stack choose this configuration. > > I have patched the usb_choose_configuration() function in file driver/usb/core/generic.c for overwrite the value with the good one. This can be changed later in the driver with usb_driver_set_configuration(). Regards, Clemens