Re: [alsa-devel] [PATCH 4/7] ALSA: core: Expand DMA buffer information

[Takashi Iwai <tiwai@suse.de>]

On Tue, 17 Dec 2019 10:58:48 +0100,
Cezary Rojewski wrote:
> 
> Update DMA buffer definition for snd_compr_runtime so it is represented
> similarly as in snd_pcm_runtime. While at it, modify
> snd_compr_set_runtime_buffer to account for newly added members.
> 
> Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
> ---
>  include/sound/compress_driver.h | 35 ++++++++++++++++++++++++---------
>  1 file changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/include/sound/compress_driver.h b/include/sound/compress_driver.h
> index bc88d6f964da..00f633c0c3ba 100644
> --- a/include/sound/compress_driver.h
> +++ b/include/sound/compress_driver.h
> @@ -23,7 +23,6 @@ struct snd_compr_ops;
>   * struct snd_compr_runtime: runtime stream description
>   * @state: stream state
>   * @ops: pointer to DSP callbacks
> - * @dma_buffer_p: runtime dma buffer pointer
>   * @buffer: pointer to kernel buffer, valid only when not in mmap mode or
>   *	DSP doesn't implement copy
>   * @buffer_size: size of the above buffer
> @@ -34,11 +33,14 @@ struct snd_compr_ops;
>   * @total_bytes_transferred: cumulative bytes transferred by offload DSP
>   * @sleep: poll sleep
>   * @private_data: driver private data pointer
> + * @dma_area: virtual buffer address
> + * @dma_addr: physical buffer address (not accessible from main CPU)
> + * @dma_bytes: size of DMA area
> + * @dma_buffer_p: runtime dma buffer pointer
>   */
>  struct snd_compr_runtime {
>  	snd_pcm_state_t state;
>  	struct snd_compr_ops *ops;
> -	struct snd_dma_buffer *dma_buffer_p;
>  	void *buffer;
>  	u64 buffer_size;
>  	u32 fragment_size;
> @@ -47,6 +49,11 @@ struct snd_compr_runtime {
>  	u64 total_bytes_transferred;
>  	wait_queue_head_t sleep;
>  	void *private_data;
> +
> +	unsigned char *dma_area;
> +	dma_addr_t dma_addr;
> +	size_t dma_bytes;
> +	struct snd_dma_buffer *dma_buffer_p;

Why do we need to have both dma_buffer_p and its values?
For consistency with PCM stream?

For PCM, dma_area, dma_addr and dma_bytes are the primary data, which
aren't necessarily set by the dma_buffer but manually set up by the
driver.

Just wondering.


Takashi
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