From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laxman Dewangan Subject: Re: [alsa-devel] [PATCH] ASoC: snd_dmaengine: add common api for pcm_mmap Date: Thu, 28 Jun 2012 18:34:02 +0530 Message-ID: <4FEC5642.9080908@nvidia.com> References: <1340866886-24432-1-git-send-email-ldewangan@nvidia.com> <4FEC3B70.5030902@metafoo.de> <20120628121816.GB21029@sirena.org.uk> <4FEC4E62.3020101@metafoo.de> <20120628122830.GJ28922@opensource.wolfsonmicro.com> <4FEC4FA9.20004@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Takashi Iwai Cc: Mark Brown , Lars-Peter Clausen , "alsa-devel@alsa-project.org" , Stephen Warren , "linux-kernel@vger.kernel.org" , "lrg@ti.com" , Marek Szyprowski List-Id: alsa-devel@alsa-project.org On Thursday 28 June 2012 06:27 PM, Takashi Iwai wrote: > At Thu, 28 Jun 2012 18:05:53 +0530, > Laxman Dewangan wrote: >> On Thursday 28 June 2012 05:58 PM, Mark Brown wrote: >>> * PGP Signed by an unknown key >>> >>> On Thu, Jun 28, 2012 at 02:30:26PM +0200, Lars-Peter Clausen wrote: >>>> On 06/28/2012 02:18 PM, Mark Brown wrote: >>>>> Oh, dear - this means we don't actually have a generic API at all. Is >>>>> there any effort being made to make this generally available? >>>> Yes there is, and in fact in next/master there is generic >>>> dma_mmap_writecombine. I'm not quite sure how it behaves on non ARM archs >>>> though. But in theory it should fallback to a normal coherent mapping. Marek >>>> did a lot of work on this, I've put him on Cc. >> So can we put the function snd_pcm_lib_writecombine_mmap() in the >> pcm_native.c and only export this api for ARM i.e. under macro #ifdef >> CONFIG_ARM so that ARM based SOCs like Tegra/epa3xx/mxs/spear can >> directly use that one? >> Or, wait for this common API until all ARCH support it? > I think it's fine to put it first in ALSA side with some ifdef. > A similar trick is already found for snd_pcm_lib_mmap_iomem. > See include/sound/pcm.h. > > But, actually it's a still question what if an architecture doesn't > support the mmap of writecombine at all. The proposed patch doesn't > allow you to know whether writecombine-mmap is possible or not on the > running architecture until you really try to call it and fail. > It's a missing piece, IMO. Lars wanted to move the buffer allocation also to common place. Then how about this? create new file and header for snd-pcm-writecombine-buffer.c/.h and put this in sound/core. Select this file compilation through config SND_PCM_WRITECOMBINE_BUFFER which will be select this config through sound/soc/xxx/Kconfig if they want to use. This will provide three apis: new, free and mmap.