[alsa-devel] mapping externally allocated Scatter Gather DMA buffers

[Jaroslav Kysela]

On Tue, 9 Nov 2010, Manu Abraham wrote:

> On Tue, Nov 9, 2010 at 5:31 PM, Jaroslav Kysela <perex at perex.cz> wrote:
>> On Tue, 9 Nov 2010, Manu Abraham wrote:
>>
>>> testbox ~ # arecord -Dhw:2,0
>>> Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
>>
>>> Any idea, why saa7231_hw_params is not getting invoked ?
>>
>> Your hw probably does not support directly 8-bit sample at 8000Hz, one
>> channel. Use 'plughw:2,0' device instead 'hw:2,0' to let alsa-lib do all
>> stream format conversions.
>
> That didn't make any difference at all.

Check your code. You probably created wrong hw_ops, looking to your code:

 	.buffer_bytes_max	= 512 * 4096,
 	.period_bytes_min	= 8192,
 	.period_bytes_max	= 8192,
 	.periods_min		= 8192,
 	.periods_max		= 8192,

It's definitely an empty configuration space.

You have buffer_bytes_max 2097152, but restricted number of periods to 
8192 and period_bytes to 8192.

8192 * 8192 = 67108864 which is not less than 2097152 (and I'm not 
counting the bytes for channels and formats). Bingo, the ALSA PCM 
code does not know what to configure.

Decrease periods_min and probably also periods_max.

 					Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>