From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Subject: Re: [PATCH] Re: 2.6.26-rc1 regression: ISA DMA broken (bisected) Date: Fri, 30 May 2008 15:43:41 -0600 Message-ID: <200805301543.42208.bjorn.helgaas@hp.com> References: <4823AAF2.7070102@keyaccess.nl> <482B38D6.5030804@keyaccess.nl> <48406E8D.8050408@keyaccess.nl> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from g5t0009.atlanta.hp.com (g5t0009.atlanta.hp.com [15.192.0.46]) by alsa0.perex.cz (Postfix) with ESMTP id 58F8A243F3 for ; Fri, 30 May 2008 23:43:40 +0200 (CEST) In-Reply-To: <48406E8D.8050408@keyaccess.nl> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Rene Herman Cc: Takashi Iwai , Andrew Morton , ALSA devel , Linux Kernel , Alan Cox List-Id: alsa-devel@alsa-project.org On Friday 30 May 2008 03:15:57 pm Rene Herman wrote: > On 14-05-08 21:09, Rene Herman wrote: > > > On 14-05-08 20:50, Bjorn Helgaas wrote: > > >> I agree, it seems a bit of a hack to use a DMA mask from the card > >> instead of from the device, since the driver should be programming > >> the device to do the DMA. > >> > >> But I know very little about pnp_card in general, so don't attach too > >> much weight to my opinion. > > > > Okay, I'll sit on this for a bit. Right now we're using a global device > > even but this is exactly about cleaning that up so couldn't convince > > myself. Will see what happens when I try to make it nice... > > It gets uglier. ALSA ISA drivers (for cards that exist both as legacy > and as ISAPnP at least) keep a merged legacy/isapnp model; PnP is used > mostly for initializing global variables that the same old legacy probe > routines then reference. This means that beyond that global resource > init step the specific struct device is no longer available. Without > restructuring too many things really only fixable through other hacks > again such as a global dma_dev[] array or some such. > > From the viewpoint of PnP itself setting the dma_mask for a pnp_card (a > pnp_dev collection) makes isolated sense so if no objections, I'll > submit the attached after all. From the ALSA side we'd then pass the > card dev (which we'd also do for isa_dev) and keep in mind that we might > want to get more specific if over time structure permits it. > > struct snd_pcm already has its own struct device * which would be the > right one here but it's setting that which gets ugly... Looks good to me. It does sound like a lot of work and possibly more risk than it's worth to fix up some of this stuff. I do still wonder whether any non-x86 architectures need similar fixes in dma_alloc_coherent(), i.e., check for dev==NULL and fall back to a 24-bit DMA mask. Acked-by: Bjorn Helgaas