The URB calculus code may eventually be moved to some other
place, like at pcm open, if it ends by needing more setups, like
working with different bit rates, or different audio latency.
So, move it into a separate routine. That also makes the code
more readable.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Pulseaudio has the bad habit of stopping a streaming audio if
a device, opened in non-block mode, waits.
It is impossible to avoid em28xx to wait, as it will send commands
via I2C, and other I2C operations may be happening (firmware
transfers, Remote Controller polling, etc). Yet, as each em28xx
subdriver locks em28xx-dev to protect the access to the hardware,
it is possible to minimize the audio glitches by returning -EAGAIN
to pulseaudio, if the lock is already taken by another subdriver.
Reported-by: Antti Palosaari <crope@iki.fi>
Tested-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
If the period size is wrong, userspace will assume a wrong delay
any may negociate an inadequate value.
The em28xx devices use 8 for URB interval, in microframes,
and the driver programs it to have 64 packets.
That means that the IRQ sampling period is 125 * 8 * 64,
with is equal to 64 ms.
So, that's the minimal latency with the current settings. It is
possible to program a lower latency, by using less than 64 packets,
but that increases the amount of bandwitdh used, and the number of
IRQ events per second.
In any case, in order to support it, the driver logic should be
changed to fill those parameters in realtime.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
The current code hardcodes the number of audio URBs, the number
of packets per URB and the maximum URB size.
This is not a good idea, as it:
- wastes more bandwidth than necessary, by using a very
large number of packets;
- those constants are bound to an specific scenario, with
a bandwidth of 48 kHz;
- don't take the maximum endpoint size into account;
- with urb->interval = 1 on xHCI, those constraints cause a "funny"
setup: URBs with 64 packets inside, with only 24 bytes total. E. g.
a complete waste of space.
Change the code to do dynamic URB audio calculus and allocation.
For now, use the same constraints as used before this patch, to
avoid regressions.
A good scenario (tested) seems to use those defines, instead:
#define EM28XX_MAX_AUDIO_BUFS 8
#define EM28XX_MIN_AUDIO_PACKETS 2
But let's not do such change here, letting the optimization to
happen on latter patches, after more tests.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Just filling urb->interval with 1 is wrong, and causes a different
behaviour with xHCI.
With EHCI, the URB size is typically 192 bytes. However, as
xHCI specifies intervals in microframes, the URB size becomes
too short (24 bytes).
With this patch, the interval will be properly initialized, and
the device will behave the same if connected into a xHCI or an
EHCI device port.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Instead of allocating/deallocating URBs and transfer buffers
every time stream is started/stopped, just do it once.
That reduces the memory allocation pressure and makes the
code that start/stop streaming a way simpler.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Instead of allocating transfer buffers with kmalloc() use
usb_alloc_coherent().
This patch should make it work also with ARM CPUs.
Reviewed-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Use the same module version on all em28xx sub-modules, and use
the same naming convention to describe the driver.
Reviewed-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Add a message with consistent prints before and after each
extension initialization, and provide a better text for module
load.
While here, add a missing sanity check for extension finish
code at em28xx-v4l extension.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Rename all USB drivers with their own directory under
drivers/media/video into drivers/media/usb and update the
building system.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
