On Thu, 16 Jan 2020 05:53:18 +0100, Keyon Jie wrote:
With today's code, we preallocate DMA buffer for substreams at pcm_new() stage, and the substream->buffer_bytes_max and substream->dma_max will save as the actually preallocated buffer size and maximum size that the dma buffer can be expanded by at hw_params() state, correspondingly.
No, it's other way round: the former, buffer_bytes_max, is the max size defined by the driver (i.e. passed in snd_pcm_hardware) and the latter, dma_max, is the max preallocation size (passed to preallocation helper).
At pcm_open() stage, the maximum constraint of HW_PARAM_BUFFER_BYTES is set to substream->buffer_bytes_max and returned to user space as the max interval of the HW_PARAM_BUFFER_BYTES, this will lead to issue that user can't choose any buffer-bytes larger than the preallocated buffer size, and the buffer reallocation will never happen actually.
Here change to use substream->dma_max as the maximum constraint of the HW_PARAM_BUFFER_BYTES and fix the issue mentioned above.
I don't think the logic in the current code you're changing is wrong. If there is any, it must be something else.
This might be rather the FIXME code found in snd_pcm_hw_constraints_complete()?
thanks,
Takashi
Signed-off-by: Keyon Jie yang.jie@linux.intel.com
sound/core/pcm_native.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index c375c41496f8..326e921006e7 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2301,7 +2301,7 @@ static int snd_pcm_hw_rule_buffer_bytes_max(struct snd_pcm_hw_params *params, struct snd_interval t; struct snd_pcm_substream *substream = rule->private; t.min = 0;
- t.max = substream->buffer_bytes_max;
- t.max = substream->dma_max; t.openmin = 0; t.openmax = 0; t.integer = 1;
-- 2.20.1