From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Cipher TLSv1:DES-CBC3-SHA:168) (Exim 3.31-VA-mm2 #1 (Debian)) id 1A6FOX-0006xq-00 for ; Sun, 05 Oct 2003 13:22:22 -0700 Received: from bay7-f106.bay7.hotmail.com ([64.4.11.106] helo=hotmail.com) by sc8-sf-mx1.sourceforge.net with esmtp (Exim 4.22) id 1A6FOW-00088s-Ct for user-mode-linux-devel@lists.sourceforge.net; Sun, 05 Oct 2003 13:22:20 -0700 From: "Steve Schmidtke" Mime-Version: 1.0 Content-Type: text/html Message-ID: Subject: [uml-devel] Re: Hostaudio module parameters Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: Date: Sun, 05 Oct 2003 20:20:19 +0000 To: blaisorblade_spam@yahoo.it Cc: user-mode-linux-devel@lists.sourceforge.net, jdike@addtoit.com

>Since hostaudio can be also a module, it's useful to specify the host dsp and

>mixer position even on module loading. So I've added two params with

>descriptions for this. The patch is straightforward and non-intrusive, so
>please apply it.

This could be abused to allow reading and writing arbitrary files on the host by loading the module with parameters within the UML.

>By the way: while testing it(I repeated this with an unpatched UML kernel)

>with mpg123, I discovered that it crackles horribly and plays very
>slowly(i.e. a second of music lasts even two or more ones). Will this ever be

>solved? Is this problem specific to me or general?

I think it's due to the dsp device being opened in blocking mode and the UML pauses while the audio data gets written out.  There is no support for async IO in the driver, so turning on O_NONBLOCK on the host file open, might speed up the app, but likely result in choppy output, and/or confuse the app with EAGAIN errors.

The answer to this is to rewrite the driver as a virtual sound card with async IO.  I may do this at some point, if no one is willing to take on the challenge.

 

Steve Schmidtke


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