Quick question
_From my copy function after I pass the buffer to HW, what would happen if i call snd_pcm_period_elapsed.
On Mon, Jun 2, 2008 at 1:37 PM, Takashi Iwai tiwai@suse.de wrote:
At Mon, 2 Jun 2008 13:26:01 +0530, Harsha priya gupta wrote:
I implemented the copy function and immediately transfered the user block
data
to the hardware.
Correct me if am wrong; .pointer implementation - passes the current buffer pointer. When the
.pointer
function returns the size of the buffer = user buffer size logically I
need to
expect the hardware to send an interrupt because buffer is consumed and I should call snd_pcm_period_elapsed after that.
what would happen if i call the snd_pcm_period_elapsed from the pointer function once the buffer is consumed from hardware. Would that be right?
This
is what i am trying to do
The logic is reversed. The pointer callback is a passive one that does nothing but returning the current h/w buffer position. This is called either from snd_pcm_period_elapsed() or at the PCM status update.
You must call snd_pcm_period_elapsed() somewhere in your driver *explicitly* at the timing that one period is finished. Usually, this is done in an IRQ handler the h/w generates at the period ("fragment", "half-buffer", or whatever) boundary.
And note that the valid value from the pointer callback is between 0 and buffer_size-1 as it handles the buffer as a ring-buffer. The value buffer_size is invalid.
Takashi
On Mon, Jun 2, 2008 at 1:02 PM, Takashi Iwai tiwai@suse.de wrote:
At Mon, 2 Jun 2008 12:39:31 +0530, Harsha priya gupta wrote: > > Can anyone give me a clue as to when i would get such an error? ... only if you give more clue what exactly you did. In general, it implies that an interrupt isn't issued properly at PCM period boundary. Takashi-- -Harsha