ALSA: firewire-lib: tune the minimum available size of PCM period
In IEC 61883-1/6, one isoc packet can transfer events up to the value of syt interval. This comes from the interval of isoc cycle. As 1394 OHCI controller can generate hardware IRQ per isoc packet, the interval is calculated as 125 usec. In IEC 61883-1/6, two ways of transmission is described; blocking and non-blocking methods. In blocking method, the sequence of packet includes 'empty' or 'NODATA' packets which include no events. In non-blocking method, the number of events per packet is variable up to the syt interval. This commit uses double of the value of syt interval as minimum available size of PCM period due to the above protocol design. Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Link: https://lore.kernel.org/r/20191017155424.885-13-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>
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