At Mon, 5 Feb 2007 10:51:16 +0100, Micha Nelissen wrote: > > Hi, > > I have a 16 bit alsa driver that allocates kernel memory, uses > SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data(GFP_KERNEL), and > specifies MMAP | MMAP_VALID et.al. The idea is that user space writes > into this mmapped memory, and from the kernel I send the data to the > sound device. > > For testing, I've modified this driver to check the values in the buffer > to be increasing 1, 2, 3, etc.. and written a test program that opens > alsa and writes these values in a buffer using snd_pcm_writei. > > I observe that some samples are from the previous iteration in the > buffer, but the surrounding samples are ok. For example with 2000 frames > buffer size, period size 500, then in the third iteration I read 2000, > 4001, 4002, ... instead of 4000, 4001, 4002, ... > > Memory test ran ok, so that's not the problem, and also linux is running > stable. > > The rate is 8 khz, and I'm not getting alsa underruns. > > Has anyone seen this behaviour before, and how to fix it ? Or, any hints > how to reproduce the alsa mmap behaviour in a smaller software stack ? Which architecture is it? It might be a memory coherency problem. Does the normal snd_pcm_writei() work as expected? Takashi ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
