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  1. 23 Jun, 2017 1 commit
    • Takashi Iwai's avatar
      ALSA: pcm: Add the explicit appl_ptr sync support · 42f94597
      Takashi Iwai authored 
      Currently x86 platforms use the PCM status/control mmaps for
transferring the PCM status and appl_ptr between kernel and
user-spaces.  The mmap is a most efficient way of communication, but
it has a drawback per its nature, namely, it can't notify the change
explicitly to kernel.

The lack of appl_ptr update notification is a problem on a few
existing drivers, but it's mostly a small issue and negligible.
However, a new type of driver that uses DSP for a deep buffer
management requires the exact position of appl_ptr for calculating the
buffer prefetch size, and the asynchronous appl_ptr update between
kernel and user-spaces becomes a significant problem for it.

How can we enforce user-space to report the appl_ptr update?  The way
is relatively simple.  Just by disabling the PCM control mmap, the
user-space is supposed to fall back to the mode using SYNC_PTR ioctl,
and the kernel gets control over that.  This fallback mode is used in
all non-x86 platforms as default, and also in the 32bit compatible
model on all platforms including x86.  It's been implemented already
over a decade, so we can say it's fairly safe and stably working.

With the help of the knowledge above, this patch introduces a new PCM
info flag SNDRV_PCM_INFO_SYNC_APPLPTR for achieving the appl_ptr sync
from user-space.  When a driver sets this flag at open, the PCM status
/ control mmap is disabled, which effectively switches to SYNC_PTR
mode in user-space side.

In this version, both PCM status and control mmaps are disabled
although only the latter, control mmap, is the target.  It's because
the current alsa-lib implementation supposes that both status and
control mmaps are always coupled, thus it handles a fatal error when
only one of them fails.

Of course, the disablement of the status/control mmaps may bring a
slight performance overhead.  Thus, as of now, this should be used
only for the dedicated devices that deserves.

Note that the disablement of mmap is a sort of workaround.  In the
later patch, we'll introduce the way to identify the protocol version
alsa-lib supports, and keep mmap working while the sync_ptr is
performed together.
Reviewed-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      42f94597
  3. 21 Jun, 2017 1 commit
  5. 20 Jun, 2017 8 commits
  7. 19 Jun, 2017 1 commit
    • Takashi Sakamoto's avatar
      ALSA: firewire-lib: Fix stall of process context at packet error · 4a9bfafc
      Takashi Sakamoto authored 
      At Linux v3.5, packet processing can be done in process context of ALSA
PCM application as well as software IRQ context for OHCI 1394. Below is
an example of the callgraph (some calls are omitted).

ioctl(2) with e.g. HWSYNC
(sound/core/pcm_native.c)
->snd_pcm_common_ioctl1()
  ->snd_pcm_hwsync()
    ->snd_pcm_stream_lock_irq
    (sound/core/pcm_lib.c)
    ->snd_pcm_update_hw_ptr()
      ->snd_pcm_udpate_hw_ptr0()
        ->struct snd_pcm_ops.pointer()
        (sound/firewire/*)
        = Each handler on drivers in ALSA firewire stack
          (sound/firewire/amdtp-stream.c)
          ->amdtp_stream_pcm_pointer()
            (drivers/firewire/core-iso.c)
            ->fw_iso_context_flush_completions()
              ->struct fw_card_driver.flush_iso_completion()
              (drivers/firewire/ohci.c)
              = flush_iso_completions()
                ->struct fw_iso_context.callback.sc
                (sound/firewire/amdtp-stream.c)
                = in_stream_callback() or out_stream_callback()
                  ->...
    ->snd_pcm_stream_unlock_irq

When packet queueing error occurs or detecting invalid packets in
'in_stream_callback()' or 'out_stream_callback()', 'snd_pcm_stop_xrun()'
is called on local CPU with disabled IRQ.

(sound/firewire/amdtp-stream.c)
in_stream_callback() or out_stream_callback()
->amdtp_stream_pcm_abort()
  ->snd_pcm_stop_xrun()
    ->snd_pcm_stream_lock_irqsave()
    ->snd_pcm_stop()
    ->snd_pcm_stream_unlock_irqrestore()

The process is stalled on the CPU due to attempt to acquire recursive lock.

[  562.630853] INFO: rcu_sched detected stalls on CPUs/tasks:
[  562.630861]      2-...: (1 GPs behind) idle=37d/140000000000000/0 softirq=38323/38323 fqs=7140
[  562.630862]      (detected by 3, t=15002 jiffies, g=21036, c=21035, q=5933)
[  562.630866] Task dump for CPU 2:
[  562.630867] alsa-source-OXF R  running task        0  6619      1 0x00000008
[  562.630870] Call Trace:
[  562.630876]  ? vt_console_print+0x79/0x3e0
[  562.630880]  ? msg_print_text+0x9d/0x100
[  562.630883]  ? up+0x32/0x50
[  562.630885]  ? irq_work_queue+0x8d/0xa0
[  562.630886]  ? console_unlock+0x2b6/0x4b0
[  562.630888]  ? vprintk_emit+0x312/0x4a0
[  562.630892]  ? dev_vprintk_emit+0xbf/0x230
[  562.630895]  ? do_sys_poll+0x37a/0x550
[  562.630897]  ? dev_printk_emit+0x4e/0x70
[  562.630900]  ? __dev_printk+0x3c/0x80
[  562.630903]  ? _raw_spin_lock+0x20/0x30
[  562.630909]  ? snd_pcm_stream_lock+0x31/0x50 [snd_pcm]
[  562.630914]  ? _snd_pcm_stream_lock_irqsave+0x2e/0x40 [snd_pcm]
[  562.630918]  ? snd_pcm_stop_xrun+0x16/0x70 [snd_pcm]
[  562.630922]  ? in_stream_callback+0x3e6/0x450 [snd_firewire_lib]
[  562.630925]  ? handle_ir_packet_per_buffer+0x8e/0x1a0 [firewire_ohci]
[  562.630928]  ? ohci_flush_iso_completions+0xa3/0x130 [firewire_ohci]
[  562.630932]  ? fw_iso_context_flush_completions+0x15/0x20 [firewire_core]
[  562.630935]  ? amdtp_stream_pcm_pointer+0x2d/0x40 [snd_firewire_lib]
[  562.630938]  ? pcm_capture_pointer+0x19/0x20 [snd_oxfw]
[  562.630943]  ? snd_pcm_update_hw_ptr0+0x47/0x3d0 [snd_pcm]
[  562.630945]  ? poll_select_copy_remaining+0x150/0x150
[  562.630947]  ? poll_select_copy_remaining+0x150/0x150
[  562.630952]  ? snd_pcm_update_hw_ptr+0x10/0x20 [snd_pcm]
[  562.630956]  ? snd_pcm_hwsync+0x45/0xb0 [snd_pcm]
[  562.630960]  ? snd_pcm_common_ioctl1+0x1ff/0xc90 [snd_pcm]
[  562.630962]  ? futex_wake+0x90/0x170
[  562.630966]  ? snd_pcm_capture_ioctl1+0x136/0x260 [snd_pcm]
[  562.630970]  ? snd_pcm_capture_ioctl+0x27/0x40 [snd_pcm]
[  562.630972]  ? do_vfs_ioctl+0xa3/0x610
[  562.630974]  ? vfs_read+0x11b/0x130
[  562.630976]  ? SyS_ioctl+0x79/0x90
[  562.630978]  ? entry_SYSCALL_64_fastpath+0x1e/0xad

This commit fixes the above bug. This assumes two cases:
1. Any error is detected in software IRQ context of OHCI 1394 context.
In this case, PCM substream should be aborted in packet handler. On the
other hand, it should not be done in any process context. TO distinguish
these two context, use 'in_interrupt()' macro.
2. Any error is detect in process context of ALSA PCM application.
In this case, PCM substream should not be aborted in packet handler
because PCM substream lock is acquired. The task to abort PCM substream
should be done in ALSA PCM core. For this purpose, SNDRV_PCM_POS_XRUN is
returned at 'struct snd_pcm_ops.pointer()'.
Suggested-by: default avatarClemens Ladisch <clemens@ladisch.de>
Fixes: e9148ddd("ALSA: firewire-lib: flush completed packets when reading PCM position")
Cc: <stable@vger.kernel.org> # 4.9+
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      4a9bfafc
  9. 16 Jun, 2017 6 commits
  11. 14 Jun, 2017 10 commits
  13. 13 Jun, 2017 1 commit
  15. 12 Jun, 2017 4 commits
    • Takashi Sakamoto's avatar
      ALSA: pcm: use %s instead of %c for format of PCM buffer tracepoints · f5abd532
      Takashi Sakamoto authored 
      As long as I know, in userspace, '%c' format on printing format for
tracepoint is replaced with '>c<' by existent tracing program; i.g.
'perf-trace' and 'trace-cmd'. This is inconvenient.

This commit replaces the format with '%s'. The length of letters in the
format string is not changed, thus this commit doesn't increase object
size.

In theory, I should work for improvements of these tracing programs, but
here I'd like to save my time to work for the other projects.
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      f5abd532
    • Takashi Sakamoto's avatar
      ALSA: pcm: add 'applptr' event of tracepoint · fccf5388
      Takashi Sakamoto authored 
      In design of ALSA PCM core, status and control data for runtime of ALSA
PCM substream are shared between kernel/user spaces by page frame
mapping with read-only attribute. Both of hardware-side and
application-side position on PCM buffer are maintained as a part of
the status data. In a view of ALSA PCM application, these two positions
can be updated by executing ioctl(2) with some commands.

There's an event of tracepoint for hardware-side position; 'hwptr'.
On the other hand, no events for application-side position. This commit
adds a new event for this purpose; 'applptr'. When the application-side
position is changed in kernel space, this event is probed with useful
information for developers.

I note that the event is not probed for all of ALSA PCM applications, When
applications are written by read/write programming scenario, the event is
surely probed. The applications execute ioctl(2) with
SNDRV_PCM_IOCTL_[READ|WRITE][N/I]_FRAMES to read/write any PCM frame, then
ALSA PCM core updates the application-side position in kernel land.
However, when applications are written by mmap programming scenario, if
maintaining the application side position in kernel space accurately,
applications should voluntarily execute ioctl(2) with
SNDRV_PCM_IOCTL_SYNC_PTR to commit the number of handled PCM frames. If
not voluntarily, the application-side position is not changed, thus the
added event is not probed.

There's a loophole, using architectures to which ALSA PCM core judges
non cache coherent. In this case, the status and control data is not mapped
into processe's VMA for any applications. Userland library, alsa-lib, is
programmed for this case. It executes ioctl(2) with
SNDRV_PCM_IOCTL_SYNC_PTR command every time to requiring the status and
control data.

ARM is such an architecture. Below is an example with serial sound interface
(ssi) on i.mx6 quad core SoC. I use v4.1 kernel released by fsl-community
with patches from VIA Tech. Inc. for VAB820, and my backport patches for
relevant features for this patchset. I use Ubuntu 17.04 from
ports.ubuntu.com as user land for armhf architecture.

$ aplay -v -M -D hw:imx6vab820sgtl5,0 /dev/urandom -f S16_LE -r 48000 --period-size=128 --buffer-size=256
Playing raw data '/dev/urandom' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono
Hardware PCM card 0 'imx6-vab820-sgtl5000' device 0 subdevice 0
Its setup is:
  stream       : PLAYBACK
  access       : MMAP_INTERLEAVED
  format       : S16_LE
  subformat    : STD
  channels     : 1
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 16
  buffer_size  : 256
  period_size  : 128
  period_time  : 2666
  tstamp_mode  : NONE
  tstamp_type  : MONOTONIC
  period_step  : 1
  avail_min    : 128
  period_event : 0
  start_threshold  : 256
  stop_threshold   : 256
  silence_threshold: 0
  silence_size : 0
  boundary     : 1073741824
  appl_ptr     : 0
  hw_ptr       : 0
mmap_area[0] = 0x76f98000,0,16 (16)

$ trace-cmd record -e snd_pcm:hwptr -e snd_pcm:applptr
$ trace-cmd report
...
60.208495: applptr: pcmC0D0p/sub0: prev=1792, curr=1792, avail=0, period=128, buf=256
60.208633: applptr: pcmC0D0p/sub0: prev=1792, curr=1792, avail=0, period=128, buf=256
60.210022: hwptr:   pcmC0D0p/sub0: IRQ: pos=128, old=1536, base=1536, period=128, buf=256
60.210202: applptr: pcmC0D0p/sub0: prev=1792, curr=1792, avail=128, period=128, buf=256
60.210344: hwptr:   pcmC0D0p/sub0: POS: pos=128, old=1664, base=1536, period=128, buf=256
60.210348: applptr: pcmC0D0p/sub0: prev=1792, curr=1792, avail=128, period=128, buf=256
60.210486: applptr: pcmC0D0p/sub0: prev=1792, curr=1792, avail=128, period=128, buf=256
60.210626: applptr: pcmC0D0p/sub0: prev=1792, curr=1920, avail=0, period=128, buf=256
60.211002: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=0, period=128, buf=256
60.211142: hwptr:   pcmC0D0p/sub0: POS: pos=128, old=1664, base=1536, period=128, buf=256
60.211146: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=0, period=128, buf=256
60.211287: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=0, period=128, buf=256
60.212690: hwptr:   pcmC0D0p/sub0: IRQ: pos=0, old=1664, base=1536, period=128, buf=256
60.212866: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=128, period=128, buf=256
60.212999: hwptr:   pcmC0D0p/sub0: POS: pos=0, old=1792, base=1792, period=128, buf=256
60.213003: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=128, period=128, buf=256
60.213135: applptr: pcmC0D0p/sub0: prev=1920, curr=1920, avail=128, period=128, buf=256
60.213276: applptr: pcmC0D0p/sub0: prev=1920, curr=2048, avail=0, period=128, buf=256
60.213654: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=0, period=128, buf=256
60.213796: hwptr:   pcmC0D0p/sub0: POS: pos=0, old=1792, base=1792, period=128, buf=256
60.213800: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=0, period=128, buf=256
60.213937: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=0, period=128, buf=256
60.215356: hwptr:   pcmC0D0p/sub0: IRQ: pos=128, old=1792, base=1792, period=128, buf=256
60.215542: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=128, period=128, buf=256
60.215679: hwptr:   pcmC0D0p/sub0: POS: pos=128, old=1920, base=1792, period=128, buf=256
60.215683: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=128, period=128, buf=256
60.215813: applptr: pcmC0D0p/sub0: prev=2048, curr=2048, avail=128, period=128, buf=256
60.215947: applptr: pcmC0D0p/sub0: prev=2048, curr=2176, avail=0, period=128, buf=256
...

We can surely see 'applptr' event is probed even if the application run
for mmap programming scenario ('-M' option and 'hw' plugin). Below is a
result of strace:

02:44:15.886382 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.887203 poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
02:44:15.887471 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.887637 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.887805 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.887969 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.888132 read(3, "..."..., 256) = 256
02:44:15.889040 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.889221 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.889431 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.889606 poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
02:44:15.889833 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.889998 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.890164 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.891048 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.891228 read(3, "..."..., 256) = 256
02:44:15.891497 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.891661 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.891829 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0
02:44:15.891991 poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
02:44:15.893007 ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x56a32b30) = 0

We can see 7 calls of ioctl(2) with SNDRV_PCM_IOCTL_SYNC_PTR per loop with
call of poll(2). 128 PCM frames are transferred per loop of one poll(2),
because the PCM substream is configured with S16_LE format and 1 channel
(2 byte * 1 * 128 = 256 bytes). This equals to the size of period of PCM
buffer. Comparing to the probed data, one of the 7 calls of ioctl(2) is
actually used to commit the number of copied PCM frames to kernel space.
The other calls are just used to check runtime status of PCM substream;
e.g. XRUN.

The tracepoint event is useful to investigate this case. I note that below
modules are related to the above sample.

 * snd-soc-dummy.ko
 * snd-soc-imx-sgtl5000.ko
 * snd-soc-fsl-ssi.ko
 * snd-soc-imx-pcm-dma.ko
 * snd-soc-sgtl5000.ko

My additional note is lock acquisition. The event is probed under acquiring
PCM stream lock. This means that calculation in the event is free from
any hardware events.
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      fccf5388
    • Takashi Sakamoto's avatar
      ALSA: pcm: unify codes to operate application-side position on PCM buffer · 66e01a5c
      Takashi Sakamoto authored 
      In a series of recent work, ALSA PCM core got some arrangements to handle
application-side position on PCM buffer. However, relevant codes still
disperse to two translation units

This commit unifies these codes into a helper function.
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      66e01a5c
    • Takashi Iwai's avatar
      ALSA: seq: Allow the modular sequencer registration · 111b0cdb
      Takashi Iwai authored 
      Many drivers bind the sequencer stuff in off-load by another driver
module, so that it's loaded only on demand.  In the current code, this
mechanism doesn't work when the driver is built-in while the sequencer
is module.  We check with IS_REACHABLE() and enable only when the
sequencer is in the same level of build.

However, this is basically a overshoot.  The binder code
(snd-seq-device) is an individual module from the sequencer core
(snd-seq), and we just have to make the former a built-in while
keeping the latter a module for allowing the scenario like the above.

This patch achieves that by rewriting Kconfig slightly.  Now, a driver
that provides the manual sequencer device binding should select
CONFIG_SND_SEQ_DEVICE in a way as
	select SND_SEQ_DEVICE if SND_SEQUENCER != n

Note that the "!=n" is needed here to avoid the influence of the
sequencer core is module while the driver is built-in.

Also, since rawmidi.o may be linked with snd_seq_device.o when
built-in, we have to shuffle the code to make the linker happy.
(the kernel linker isn't smart enough yet to handle such a case.)
That is, snd_seq_device.c is moved to sound/core from sound/core/seq,
as well as Makefile.

Last but not least, the patch replaces the code using IS_REACHABLE()
with IS_ENABLED(), since now the condition meets always when enabled.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      111b0cdb
  17. 11 Jun, 2017 2 commits
  19. 09 Jun, 2017 6 commits
    • Takashi Iwai's avatar
      ALSA: synth: Select snd-emux-synth explicitly · 82721155
      Takashi Iwai authored 
      Instead of the non-standard way to enable the build of snd-emux-synth
module inside Makefile, rewrite Kconfig to select the item explicitly
from each driver (sbawe and emu10k1).  This is the standard way.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      82721155
    • Takashi Iwai's avatar
      ALSA: seq: Reorganize kconfig and build · 0181307a
      Takashi Iwai authored 
      This is a slightly intensive rewrite of Kconfig and Makefile about
ALSA sequencer stuff.

The first major change is that the kconfig items for the sequencer are
moved to sound/core/seq/Kconfig.  OK, that's easy.

The substantial change is that, instead of hackish top-level module
selection in Makefile, we define a Kconfig item for each sequencer
module.  The driver that requires such sequencer components select
exclusively the kconfig items.  This is more straightforward and
standard way.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      0181307a
    • Takashi Iwai's avatar
      ALSA: seq: Allow the tristate build of OSS emulation · 3d774d5e
      Takashi Iwai authored 
      Currently OSS sequencer emulation is tied with ALSA sequencer core,
both are built in the same level; i.e. when CONFIG_SND_SEQUENCER=y,
the OSS sequencer emulation is also always built-in, even though the
functionality can be built as an individual module.

This patch changes the rule and allows users to build snd-seq-oss
module while others are built-in.  Essentially, it's just a few simple
changes in Kconfig and Makefile.  Some driver codes like opl3 need to
convert from the simple ifdef to IS_ENABLED().  But that's all.

You might wonder how about the dependency: right, it can be messy, but
it still works.  Since we rewrote the sequencer binding with the
standard bus, the driver can be bound at any time on demand.  So, the
synthesizer driver module can be loaded individually from the OSS
emulation core before/after it.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      3d774d5e
    • Takashi Iwai's avatar
      ALSA: Make CONFIG_SND_OSSEMUL user-selectable · eb3b705a
      Takashi Iwai authored 
      Currently CONFIG_SND_OSSEMUL is selected by each config like
CONFIG_SND_PCM_OSS.  But, as see in the raw MIDI code that is built
conditionally with CONFIG_SND_OSSEMUL, we should rather make
CONFIG_SND_OSSEMUL user-selectable as the top kconfig item, and leave
the rest depending on it.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      eb3b705a
    • Takashi Sakamoto's avatar
      ALSA: pcm: use friendly name for id of PCM substream in trace print · 6baca010
      Takashi Sakamoto authored 
      Use the same print format of snd_pcm_debug_name() for userspace tracing
program.
Suggested-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      6baca010
    • Takashi Sakamoto's avatar
      ALSA: pcm: add tracepoints for final selection process of hardware parameters · 7b8a54af
      Takashi Sakamoto authored 
      Results of ioctl(2) with SNDRV_PCM_IOCTL_HW_REFINE and
SNDRV_PCM_IOCTL_HW_PARAMS are different, because the latter has single
value for several parameters; e.g. channels of PCM substream. Selection
of the single value is done independently of application of constraints.
It's helpful for developers to trace the selection process.

This commit adds tracepoints to snd_pcm_hw_params_choose() for the
purpose.
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
      7b8a54af
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