Hello James, Thanks a lot....Just a typo error for the period_bytes_min and period_bytes_max in my mail.....
Now that my FIFO is 64 bytes and if I need an interrupt to the CPU for FIFO being half-empty (i.e 32 bytes = 16 16-bit samples), would it be right to set the periods_min = periods_max = 32?
Regards, Aadish
On Wed, Jun 23, 2010 at 11:15 PM, James Courtier-Dutton james.dutton@gmail.com wrote:
On 23 June 2010 18:22, Adish Kuvelker adkuvi@gmail.com wrote:
Hello,
I am developing a ALSA driver for the AtlasIII AC'97 Controller. The AC'97 Controller FIFO is arranged as 16 32-bit entries. My PCM data would be 16-bit samples and the driver will cater to 2-front channel audio. I have configured the snd_pcm_hardware members as follows: .formats = SNDDRV_PCM_FMTBIT_S16_LE .period_bytes_max = 4, .period_bytes_min = 64, As I would need a minimum of 4-byte sample to be transferred and the "period_bytes_max" value has been set considering the maximum size of the FIFO in bytes. Is my understanding correct in doing these settings?
Secondly, I am having slight problems in understanding the "snd_pcm_hardware" members periods_min and periods_max. Can anyone throw some more light on this in addition to what is explained in the "Writing an Audio Driver"?
max should = 64 min should = 4
periods_min and periods_max is dependent on when the sound card interrupts the CPU. So, if the CPU gets an interrupt once every 16 samples, then periods_min = periods_max = 1 If the sound card does not interrupt the CPU at all, you have to provide a method to notify the CPU when to next fill the FIFO.