Hi all, I am trying to fix (improve?) a driver for an embedded ARM device I bought months ago, and for some reasons some ALSA applications work fine while other ones don't... Looking at the driver I got, I noticed that the info field in the snd_pcm_hardware_t struct just defines: SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_PAUSE while the info in the tutorial "writing an alsa driver" defines: SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER | SNDRV_PCM_INFO_MMAP_VALID Furthermore, the driver defines a copy callback (actually 2, one for playback and one for capture), where it copies the data from the use space to the dma buffer. Since the dma buffer was preallocated with snd_pcm_lib_preallocate_pages_for_all and is accessible from the "outside", I wonder why the original author did this... I have some questions for you gurus: - what is the difference between SNDRV_PCM_INFO_MMAP and SNDRV_PCM_INFO_MMAP_VALID? What is SNDRV_PCM_INFO_BLOCK_TRANSFER? - The code calls snd_pcm_lib_preallocate_pages_for_all function as following: /* allocate the pcm(DMA) memory */ ret = snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,0, 4*128*1024, 4*128*1024); is the DMA_TYPE right for an ARM device? Is NULL a correct value for data in this case? - In case I get rid of the copy callback, how do I specify the format of the stream? How does Where can I find an example for that? Thanks a lot Andrea __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
