From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759249AbYE1Aqg (ORCPT ); Tue, 27 May 2008 20:46:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754645AbYE1Aq1 (ORCPT ); Tue, 27 May 2008 20:46:27 -0400 Received: from wf-out-1314.google.com ([209.85.200.168]:62442 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754204AbYE1Aq0 (ORCPT ); Tue, 27 May 2008 20:46:26 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=dLcwODW4eD4NwR4Tc5pp8p6Fnc609IYSTTQstfkc0l7OGhGtFLi/eJfBImSXS9xddSob4k55iXm4odwV2FQ+V4aC9hkh9OUZlwtfRhPOeQqwAEZkpFAi5gmwbbATRtE61YmfjZ63yS2VFE+oTRcGoHfNbeeUiOmAf8LfOtGbOeQ= Message-ID: <412bdbff0805271746x3db9ae28h3c0f0b565f50d4c6@mail.gmail.com> Date: Tue, 27 May 2008 20:46:22 -0400 From: "Devin Heitmueller" To: "Andy Walls" Subject: Re: [PATCH] video4linux: Push down the BKL Cc: "Mauro Carvalho Chehab" , "Alan Cox" , video4linux-list@redhat.com, linux-kernel@vger.kernel.org, "Alan Cox" , "Jonathan Corbet" In-Reply-To: <1211932138.3197.29.camel@palomino.walls.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080522223700.2f103a14@core> <20080526220154.GA15487@devserv.devel.redhat.com> <20080527101039.1c0a3804@gaivota> <20080527094144.1189826a@bike.lwn.net> <20080527133100.6a9302fb@gaivota> <20080527103755.1fd67ec1@bike.lwn.net> <20080527155942.7693c360@gaivota> <412bdbff0805271226t41fe55b0jd0b8e3c737f34734@mail.gmail.com> <20080527180048.6a27dbf7@gaivota> <1211932138.3197.29.camel@palomino.walls.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Andy, On Tue, May 27, 2008 at 7:48 PM, Andy Walls wrote: > MythTV's mythbackend can open both sides of the card at the same time > and the cx18 driver supports it. On my HVR-1600, MythTV may have the > digital side of the card open pulling EPG data off of the ATSC > broadcasts, when I open up the MythTV frontend and start watching live > TV on the analog side of the card. MythTV also supports > Picture-in-Picture using both the analog and digital parts of the > HVR-1600. In this case, what you see as a 'feature' in MythTV is actually a problem in our case. While the HVR-1600 can support this scenario, the HVR-950 can only use one or the other (the em28xx chip uses GPIOs to enable the demodulator and presumably you should never have both demodulators enabled at the same time). Because of this we need a lock. If MythTV only opened one device or the other at a time, we could put the lock on the open() call, but since MythTV opens both simultaneously even though it may only be using one, we would need a much more granular lock. Certainly I'm not blaming MythTV for this behavior, but it will make the locking much more complicated in some hybrid devices. -- Devin J. Heitmueller http://www.devinheitmueller.com AIM: devinheitmueller