On Mon, 17 May 2010, Jassi Brar wrote:
On Mon, May 17, 2010 at 8:16 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote:
Jassi Brar wrote:
I am in favor of support variable hw_interrupt at lowest level, i.e, in
ring buffer driver, instead of disabling hw_interrupt altogether.
Removing the constant-sized periods restriction would certainly be
useful. However, it doesn't look as if anybody has the time to redesign
the ALSA API, the kernel framework and all the drivers.
No need to redesign ALSA API and certainly no need to change _any_ driver,
just like this interrupt disable call is optional so would period resize be.
I only ask to make this newly added call as period-resize rather than
a special case of period-disable.
This is very good point. But I have two comments:
1) Period-disable function is OK, but it should not have a name "no
period irq": SNDRV_PCM_INFO_PERIOD_DISABLE or DISABLE_PERIOD looks
better. This change does imply to set the period size automatically in
the driver - probably to highest value (applications cannot choose/set
the period size in this operation mode - it's useless anyway).
2) The avail_min parameter in sw_params was overlooked. The lowlevel
drivers can use this value to compute the wake-up point and set hw
appropriately, to do wake-up at requested time. We can add a support
functions like "return how many samples are expected to be transferred
for next wake-up point" to linux/sound/pcm.h. In case when this value
is high, no interrupts (wake ups) will be processed in the driver. If
hardware cannot do the precise transfers, we can program a system
timer as the wake-up source.
Jaroslav
-----
Jaroslav Kysela <perex@xxxxxxxx>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.
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