[alsa-devel] Can I mmap buffer allocated using SNDRV_DMA_TYPE_CONTINUOUS?
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 * 1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
On 7/11/07, Pharaoh . pharaoh137@gmail.com wrote:
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 * 1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
I dont think it can be mmapped. -pharaoh.
At Wed, 11 Jul 2007 18:17:49 +0530, Pharaoh . wrote:
On 7/11/07, Pharaoh . pharaoh137@gmail.com wrote:
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 * 1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
I dont think it can be mmapped.
It can be basically, but not on all architectures. For example, ARM has a problem with coherency.
Takashi
okay, I am on ARM..so better I do not use preallocation scheme with CONTINUOUS flag in case I want to mmap my dma buffer. In fact, I tried mmaping it, but it didn't work as expected.
On 7/12/07, Takashi Iwai tiwai@suse.de wrote:
At Wed, 11 Jul 2007 18:17:49 +0530, Pharaoh . wrote:
On 7/11/07, Pharaoh . pharaoh137@gmail.com wrote:
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 * 1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
I dont think it can be mmapped.
It can be basically, but not on all architectures. For example, ARM has a problem with coherency.
Takashi
At Thu, 12 Jul 2007 19:24:24 +0530, Pharaoh . wrote:
okay, I am on ARM..so better I do not use preallocation scheme with CONTINUOUS flag in case I want to mmap my dma buffer. In fact, I tried mmaping it, but it didn't work as expected.
On ARM, the mmap support is a bit tricky, so far. The preallocation itself should work with SNDRV_DMA_TYPE_TYPE_DEV. But you'd need the mmap PCM ops to call dma_mmap_coherent() there instead of the default ALSA mmap handler.
Takashi
On 7/12/07, Takashi Iwai tiwai@suse.de wrote:
At Wed, 11 Jul 2007 18:17:49 +0530, Pharaoh . wrote:
On 7/11/07, Pharaoh . pharaoh137@gmail.com wrote:
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS, snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 * 1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
I dont think it can be mmapped.
It can be basically, but not on all architectures. For example, ARM has a problem with coherency.
Takashi
Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
Okay got it...I am currently using the mmap APIs given in arm/mm/consistant.c and they seem to work as expected. Basically I am not preallocating using ALSA provided API, rather I am using dma allocation functions given in the same file and the buffer mmaps well.
-pharaoh.
On 7/12/07, Takashi Iwai tiwai@suse.de wrote:
At Thu, 12 Jul 2007 19:24:24 +0530, Pharaoh . wrote:
okay, I am on ARM..so better I do not use preallocation scheme with CONTINUOUS flag in case I want to mmap my dma buffer. In fact, I tried mmaping it, but it didn't work as expected.
On ARM, the mmap support is a bit tricky, so far. The preallocation itself should work with SNDRV_DMA_TYPE_TYPE_DEV. But you'd need the mmap PCM ops to call dma_mmap_coherent() there instead of the default ALSA mmap handler.
Takashi
On 7/12/07, Takashi Iwai tiwai@suse.de wrote:
At Wed, 11 Jul 2007 18:17:49 +0530, Pharaoh . wrote:
On 7/11/07, Pharaoh . pharaoh137@gmail.com wrote:
Hi, I have allocated the DMA buffer using snd_pcm_lib_malloc_pages() and it was preallocated as:
snd_pcm_lib_preallocate_pages_for_all(pcm,
SNDRV_DMA_TYPE_CONTINUOUS,
snd_dma_continuous_data (GFP_KERNEL), 128 * 1024, 128 *1024);
Can I mmap such a dma buffer? I think yes...
-pharaoh.
I dont think it can be mmapped.
It can be basically, but not on all architectures. For example, ARM has a problem with coherency.
Takashi
Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
participants (2)
-
Pharaoh . -
Takashi Iwai