From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guilhem Tardy Subject: Re: documentation Date: Wed, 24 Apr 2002 12:32:26 -0700 (PDT) Sender: alsa-devel-admin@lists.sourceforge.net Message-ID: <20020424193226.2349.qmail@web11503.mail.yahoo.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: Errors-To: alsa-devel-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: Takashi Iwai Cc: alsa-devel@lists.sourceforge.net List-Id: alsa-devel@alsa-project.org > > What is required from my part to support memory mapping from the driver > > to the application? Would this be supported through the OSS compatibility > > layer, too? > > hmm... mmap without dma? > how do you transfer the data on buffer to hardware? The card doesn't support DMA, yet. Data is transferred to/from the buffer by the driver copying 32-bit chunks. Those buffers were allocated by the MMAP, today through the V4Lv2 API (this is an audio+video card). > the copy and silence ops are called when write() is called (more > exactly on alsa it's ioctl) - the thread writing to the device does > actually work like DMA. on mmap mode, there is no such one. so you > need an extra thread (or if it's not too heavy then tasklet might be > available) anyway. Having checked the brief documentation you referred to (http://www.alsa-project.org/alsa-doc/alsa-lib/), I guess using the direct audio buffer to communicate with the device means DMA+MMAP. I would like to do the same thing, but have the driver actually copy data to/from the device. What do you call "mmap mode" above? Is there any other documentation more specific to driver development? Guilhem. __________________________________________________ Do You Yahoo!? Yahoo! Games - play chess, backgammon, pool and more http://games.yahoo.com/