Hello Takashi, I am developing a DMA Controller driver to service the PCM out data to the Audio controller on the arm-based ATLASIII procesor. In case you need any more information on the architecture I can pass. Since the DMA isn't on PCI bus I am pre-allocation continuous memero using the "snd_pcm_lib_preallocate_pages_for_all" passing SNDDRV_DMA_TYPE_DEV and "snd_dma_continuous_data" as appropriate parameters. Would I still have to set the dma_addr value in my driver? Regards; Aadish On Thu, Jun 24, 2010 at 12:07 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > At Thu, 24 Jun 2010 03:50:17 +0530, > Adish Kuvelker wrote: >> >> Hello, >> >> I am trying to allocate memory for DMA buffer through >> "snd_pcm_lib_malloc_pages" in hw_params callout function, with prior >> use of "snd_pcm_lib_preallocate_pages_for_all". The chapter on PCM >> Interface in "writing an ALSA driver" states that if the standard >> function "snd_pcm_lib_malloc_pages" is use for allocating the DMA >> buffers then the DMA fields of dma_addr, dma_area, dma_bytes are set >> by the ALSA middle layer. >> >> However my code walk through didn't point me to the area where this >> physical memory setting is done. My DMA channel is not serving a PCI >> device. I would be very grateful if any of you guys can point me to >> the code where this settings get done by calling >> "snd_pcm_lib_malloc_pages". > > snd_pcm_lib_*_pages() works only with the preallocated buffers, and > the pre-allocation can be done with the generic struct device, as long > as the device (bus) supports dma_alloc_coherent() properly. > > But this can be pretty arch-specific, so better to clarify more your > hardware if you need detailed answers... > > > Takashi > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
