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 19:30:57 +0530 Message-ID: <4FEC6399.5050505@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> <4FEC5642.9080908@nvidia.com> <4FEC5DC7.5060600@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 07:21 PM, Takashi Iwai wrote: > At Thu, 28 Jun 2012 19:06:07 +0530, > Laxman Dewangan wrote: > >>>> 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. >>> Way too much hustles than necessary... >> Ooh no. :-( I had taken the idea from snd_dmaengine_pcm driver. >> Bit I like to hear simple way which solves the purpose. > As Lars suggested, a simple ifdef should suffice for now. > With the upcoming generic dma_mmap_writecombine() stuff, it'd be even > simpler in future. > > But, still we need to be careful about this. As mentioned, there is > no flag to know the possibility of writecombine mmap beforehand. > It'd be nice if we have either a compile-time or a run-time flag / > function to check that. Then the driver can also expose the mmap > capability to user-space depending on the flag. Yaah, this seems really simple. Thanks for suggestion. If I understand it fully, the new apis will be declare in sound/pcm.h, implement it in pcm_native.c and use the config variable CONFIG_SND_PCM_WRITECOMBINE_BUFFER for ifdef. This will be selected in required sound/soc driver so they can use it like powerpc (for fsl) and ARM arch based soc.