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2014-04-16ALSA: pcm: 'BUG:' message unnecessarily triggers kerneloopsTim Gardner
BugLink: http://bugs.launchpad.net/bugs/1305480 The kerneloops-daemon scans dmesg for common crash signatures, among which is 'BUG:'. The message emitted by the PCM library is really a warning, so the most expedient thing to do seems to be to change the string. Signed-off-by: Tim Gardner <tim.gardner@canonical.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2014-03-13Merge tag 'asoc-v3.15' of ↵Takashi Iwai
git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-next ASoC: Updates for v3.15 Quite a busy release for ASoC this time, more on janitorial work than exciting new features but welcome nontheless: - Lots of cleanups from Takashi for enumerations; the original API for these was error prone so he's refactored lots of code to use more modern APIs which avoid issues. - Elimination of the ASoC level wrappers for I2C and SPI moving us closer to converting to regmap completely and avoiding some randconfig hassle. - Provide both manually and transparently locked DAPM APIs rather than a mix of the two fixing some concurrency issues. - Start converting CODEC drivers to use separate bus interface drivers rather than having them all in one file helping avoid dependency issues. - DPCM support for Intel Haswell and Bay Trail platforms. - Lots of work on improvements for simple-card, DaVinci and the Renesas rcar drivers. - New drivers for Analog Devices ADAU1977, TI PCM512x and parts of the CSR SiRF SoC.
2014-02-20ALSA: Export snd_pcm_constraint_mask64()Mark Brown
Allow modules to use it, fixing a build failure when the newly added ADAU1977 driver is built as a module. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Mark Brown <broonie@linaro.org> Acked-by: Takashi Iwai <tiwai@suse.de>
2014-02-14ALSA: pcm: Use standard printk helpersTakashi Iwai
Use dev_err() & co as much as possible. If not available (no device assigned at the calling point), use pr_xxx() helpers instead. For simplicity, introduce new helpers for pcm stream, pcm_err(), etc. Signed-off-by: Takashi Iwai <tiwai@suse.de>
2013-12-17ALSA: Add SNDRV_PCM_STATE_PAUSED case in wait_for_avail functionJongHo Kim
When the process is sleeping at the SNDRV_PCM_STATE_PAUSED state from the wait_for_avail function, the sleep process will be woken by timeout(10 seconds). Even if the sleep process wake up by timeout, by this patch, the process will continue with sleep and wait for the other state. Signed-off-by: JongHo Kim <furmuwon@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2013-08-19ALSA: pcm: Use snd_printd_ratelimit()Tim Gardner
The use of snd_printd_ratelimit() supresses superfluous output from printk_ratelimit() when CONFIG_SND_DEBUG is not defined. For example, [ 43.753692] snd_pcm_update_hw_ptr0: 26 callbacks suppressed [ 48.822131] snd_pcm_update_hw_ptr0: 25 callbacks suppressed [ 53.894953] snd_pcm_update_hw_ptr0: 25 callbacks suppressed [ 58.997761] snd_pcm_update_hw_ptr0: 25 callbacks suppressed [ 64.100952] snd_pcm_update_hw_ptr0: 25 callbacks suppressed fills the log even when no debug output is actually produced. Cc: Jaroslav Kysela <perex@perex.cz> Cc: Takashi Iwai <tiwai@suse.de> Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: Yacine Belkadi <yacine.belkadi.1@gmail.com> Signed-off-by: Tim Gardner <tim.gardner@canonical.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2013-05-24ALSA: Constify the snd_pcm_substream struct ops fieldLars-Peter Clausen
The ops field of the snd_pcm_substream struct is never modified inside the ALSA core. Making it const allows drivers to declare their snd_pcm_ops struct as const. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2013-03-12ALSA: add/change some comments describing function return valuesYacine Belkadi
script/kernel-doc reports the following type of warnings (when run in verbose mode): Warning(sound/core/init.c:152): No description found for return value of 'snd_card_create' To fix that: - add missing descriptions of function return values - use "Return:" sections to describe those return values Along the way: - complete some descriptions - fix some typos Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-10-23ALSA: core: add hooks for audio timestampsPierre-Louis Bossart
ALSA did not provide any direct means to infer the audio time for A/V sync and system/audio time correlations (eg. PulseAudio). Applications had to track the number of samples read/written and add/subtract the number of samples queued in the ring buffer. This accounting led to small errors, typically several samples, due to the two-step process. Computing the audio time in the kernel is more direct, as all the information is available in the same routines. Also add new .audio_wallclock routine to enable fine-grain synchronization between monotonic system time and audio hardware time. Using the wallclock, if supported in hardware, allows for a much better sub-microsecond precision and a common drift tracking for all devices sharing the same wall clock (master clock). Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-10-23ALSA: core: keep track of boundary wrap-aroundPierre-Louis Bossart
Keep track of boundary crossing when hw_ptr exceeds boundary limit and wraps-around. This will help keep track of total number of frames played/received at the kernel level Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-09-13ALSA: Fix leftover chmap UNKNOWN -> MONO conversionsTakashi Iwai
A few files have been slipped from the previous commit to add MONO channel type. Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-09-11ALSA: pcm - Use UNKNOWN chmap for mono streamsTakashi Iwai
In general, mono streams have no dedicated speaker assignment, thus they should be rather marked as UNKNOWN position. Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-09-06ALSA: Remove VOLATILE flag from chmap ctlsTakashi Iwai
The VOLATILE flag was added to control elements by snd_pcm_add_chmap_ctls() just because I didn't want to have a side-effect of "alsactl restore". But now the set operation doesn't allow to change the value unless the PCM stream is in PREAPRED state, there is no reason to keep this flag. Let's rip it off. Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-09-06ALSA: PCM: channel mapping API implementationTakashi Iwai
This patch implements the basic data types for the standard channel mapping API handling. - The definitions of the channel positions and the new TLV types are added in sound/asound.h and sound/tlv.h, so that they can be referred from user-space. - Introduced a new helper function snd_pcm_add_chmap_ctls() to create control elements representing the channel maps for each PCM (sub)stream. - Some standard pre-defined channel maps are provided for convenience. Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-07-05ALSA: pcm: Make constraints lists constMark Brown
They aren't modified by the core so the drivers can declare them const. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-05-23ALSA: core: group read of pointer, tstamp and jiffiesPierre-Louis Bossart
Group read of hw_ptr, tstamp and jiffies in a sequence for better correlation. Previous code took timestamp at the end, which could introduce delays between audio time and system time. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-05-11ALSA: pcm - Optimize the call of snd_pcm_update_hw_ptr() in read/write loopTakashi Iwai
In the PCM read/write loop, the driver calls snd_pcm_update_hw_ptr() at each time at the beginning of the loop. Russell King reported that this hogs CPU significantly. The current code assumes that the pointer callback is very fast and cheap, also not too much fine grained. It's not true in all cases. When the pointer advances short samples while the read/write copy has been performed, the driver updates the hw_ptr and gets avail > 0 again. Then it tries to read/write these small chunks. This repeats until the avail really gets to zero. For avoiding this situation, a simple workaround is to call snd_pcm_update_hw_ptr() only once at starting the loop, assuming that the read/write copy is performed fast enough. If the available count becomes short, it goes to snd_pcm_wait_avail() anyway, and this processes right. Tested-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2012-03-15ALSA: pcm: Constify the list in snd_pcm_hw_constraint_listMark Brown
Allows the constraint lists to be declared const by drivers which seems reasonable; there's plenty of other constification we could do if we were being complete but this was easy and quick. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-10-31sound: Add export.h for THIS_MODULE/EXPORT_SYMBOL where neededPaul Gortmaker
These aren't modules, but they do make use of these macros, so they will need export.h to get that definition. Previously, they got it via the implicit module.h inclusion. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-09-20ALSA: pcm: add snd_pcm_hw_rule_noresample()Clemens Ladisch
Add a helper function to allow drivers to disable hardware resampling when the application has specified the SNDRV_PCM_HW_PARAMS_NORESAMPLE flag. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-09-15ALSA: pcm - fix race condition in wait_for_avail()Arjan van de Ven
wait_for_avail() in pcm_lib.c has a race in it (observed in practice by an Intel validation group). The function is supposed to return once space in the buffer has become available, or if some timeout happens. The entity that creates space (irq handler of sound driver and some such) will do a wake up on a waitqueue that this function registers for. However there are two races in the existing code 1) If space became available between the caller noticing there was no space and this function actually sleeping, the wakeup is missed and the timeout condition will happen instead 2) If a wakeup happened but not sufficient space became available, the code will loop again and wait for more space. However, if the second wake comes in prior to hitting the schedule_timeout_interruptible(), it will be missed, and potentially you'll wait out until the timeout happens. The fix consists of using more careful setting of the current state (so that if a wakeup happens in the main loop window, the schedule_timeout() falls through) and by checking for available space prior to going into the schedule_timeout() loop, but after being on the waitqueue and having the state set to interruptible. [tiwai: the following changes have been added to Arjan's original patch: - merged akpm's fix for waitqueue adding order into a single patch - reduction of duplicated code of avail check ] Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-07-24ALSA: Make snd_pcm_debug_name usable outside pcm_libEliot Blennerhassett
Formatting a PCM name is useful for module debug too. Add snd_prefix when making function public. [minor coding-style fixes by tiwai] Signed-off-by: Eliot Blennerhassett <eblennerhassett@audioscience.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-05-26ALSA: PCM - Don't check DMA time-out too shortlyTakashi Iwai
When the PCM period size is set larger than 10 seconds, currently the PCM core may abort the operation with DMA-error due to the fixed timeout for 10 seconds. A similar problem is seen in the drain operation that has a fixed timeout of 10 seconds, too. This patch fixes the timeout length depending on the period size and rate, also including the consideration of no_period_wakeup flag. Reported-by: Raymond Yau <superquad.vortex2@gmail.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-05-19ALSA: sound, core, pcm_lib: fix xrun_logBen Gardiner
The xrun_log function was augmented with the in_interrupt parameter whereas the empty macro definition used when xrun logging is disabled was not. Add a third parameter to the empty macro definition so as to not cause compiler errors when xrun logging (CONFIG_SND_PCM_XRUN_DEBUG) is disabled. Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-05-18ALSA: sound, core, pcm_lib: xrun_log: log also in_interruptBen Gardiner
When debugging pcm drivers I found the "period" or "hw" prefix printed by either XRUN_DEBUG_PERIODUPDATE or XRUN_DEBUG_PERIODUPDATE events, respectively to be very useful is observing the interplay between interrupt-context updates and syscall-context updates. Similarly, when debugging overruns with XRUN_DEBUG_LOG it is useful to see the context of the last 10 positions. Add an in_interrupt member to hwptr_log_entry which stores the value of the in_interrupt parameter of snd_pcm_update_hw_ptr0 when the log entry is created. Print a "[Q]" prefix when dumping the log entries if in_interrupt was true. Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-04-01ALSA: pcm: fix infinite loop in snd_pcm_update_hw_ptr0()Kelly Anderson
When period interrupts are disabled, snd_pcm_update_hw_ptr0() compares the current time against the time estimated for the current hardware pointer to detect xruns. The somewhat fuzzy threshold in the while loop makes it possible that hdelta becomes negative; the comparison being done with unsigned types then makes the loop go through the entire 263 negative range, and, depending on the value, never reach an unsigned value that is small enough to stop the loop. Doing this with interrupts disabled results in the machine locking up. To prevent this, ensure that the loop condition uses signed types for both operands so that the comparison is correctly done. Many thanks to Kelly Anderson for debugging this. Reported-by: Nix <nix@esperi.org.uk> Reported-by: "Christopher K." <c.krooss@googlemail.com> Reported-and-tested-by: Kelly Anderson <kelly@silka.with-linux.com> Signed-off-by: Kelly Anderson <kelly@silka.with-linux.com> [cl: remove unneeded casts; use a temp variable] Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Cc: 2.6.38 <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2011-01-13Merge branch 'topic/misc' into for-linusTakashi Iwai
2010-12-21ALSA: pcm: remember to always call va_end() on stuff that we va_start()Jesper Juhl
The Coverity checker spotted that we do not always remember to call va_end() on 'args' in failure paths in snd_pcm_hw_rule_add(). Here's a patch to fix that up (compile tested only) - it also removes some annoying trailing whitespace that caught my eye while I was in the area.. Signed-off-by: Jesper Juhl <jj@chaosbits.net> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-11-22ALSA: pcm: optimize xrun detection in no-period-wakeup modeClemens Ladisch
Add a lightweight condition on top of the xrun checking so that we can avoid the division when the application is calling the update function often enough. Suggested-by: Jaroslav Kysela <perex@perex.cz> Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-11-22ALSA: pcm: detect xruns in no-period-wakeup modeClemens Ladisch
When period wakeups are disabled, successive calls to the pointer update function do not have a maximum allowed distance, so xruns cannot be detected with the pointer value only. To detect xruns, compare the actually elapsed time with the time that should have theoretically elapsed since the last update. When the hardware pointer has wrapped around due to an xrun, the actually elapsed time will be too big by about hw_ptr_buffer_jiffies. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-11-22ALSA: pcm: support for period wakeup disablingClemens Ladisch
This patch allows to disable period interrupts which are not needed when the application relies on a system timer to wake-up and refill the ring buffer. The behavior of the driver is left unchanged, and interrupts are only disabled if the application requests this configuration. The behavior in case of underruns is slightly different, instead of being detected during the period interrupts the underruns are detected when the application calls snd_pcm_update_avail, which in turns forces a refresh of the hw pointer and shows the buffer is empty. More specifically this patch makes a lot of sense when PulseAudio relies on timer-based scheduling to access audio devices such as HDAudio or Intel SST. Disabling interrupts removes two unwanted wake-ups due to period elapsed events in low-power playback modes. It also simplifies PulseAudio voice modules used for speech calls. To quote Lennart "This patch looks very interesting and desirable. This is something have long been waiting for." Support for this in hardware drivers is optional. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@intel.com> Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-11-22ALSA: sound/core/pcm_lib.c: Remove unnecessary semicolonsJoe Perches
Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-08-18ALSA: pcm midlevel code - add time check for double interrupt acknowledgeJaroslav Kysela
The current code in pcm_lib.c do all checks using only the position in the ring buffer. Unfortunately, where the interrupts gets delayed or merged into one, we need another timing source to check when the buffer size boundary overlaps to avoid the wrong updating of the ring buffer pointers. This code uses jiffies to check the right time window without any performance impact. Signed-off-by: Jaroslav Kysela <perex@perex.cz> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-07-19ALSA: pcm core - add a safe check to the silence filling functionJaroslav Kysela
In situation when appl_ptr is far greater then hw_ptr, the hw_avail value can be greater than buffer_size. Check for this. Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-06-28ALSA: pcm_lib: avoid timing jitter in snd_pcm_read/write()David Dillow
When using poll() to wait for the next period -- or avail_min samples -- one gets a consistent delay for each system call that is usually just a little short of the selected period time. However, When using snd_pcm_read/write(), one gets a jittery delay that alternates between less than a millisecond and approximately two period times. This is caused by snd_pcm_lib_{read,write}1() transferring any available samples to the user's buffer and adjusting the application pointer prior to sleeping to the end of the current period. When the next period interrupt occurs, there is then less than avail_min samples remaining to be transferred in the period, so we end up sleeping until a second period occurs. This is solved by using runtime->twake as the number of samples needed for a wakeup in addition to selecting the proper wait queue to wake in snd_pcm_update_state(). This requires twake to be non-zero when used by snd_pcm_lib_{read,write}1() even if avail_min is zero. Signed-off-by: Dave Dillow <dave@thedillows.org> Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-05-25ALSA: pcm: fix delta calculation at boundary wraparoundClemens Ladisch
In the cleanup of the hw_ptr update functions in 2.6.33, the calculation of the delta value was changed to use the modulo operator to protect against a negative difference due to the pointer wrapping around at the boundary. However, the ptr variables are unsigned, so a negative difference would result in the two complement's value which has no relation to the actual difference relative to the boundary; the result is typically some value near LONG_MAX-boundary. Furthermore, even if the modulo operation would be done with signed types, the result of a negative dividend could be negative. The invalid delta value is then caught by the following checks, but this means that the pointer update is ignored. To fix this, use a range check as in the other pointer calculations. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-05-21ALSA: pcm: fix the fix of the runtime->boundary calculationClemens Ladisch
Commit 7910b4a1db63fefc3d291853d33c34c5b6352e8e in 2.6.34 changed the runtime->boundary calculation to make this value a multiple of both the buffer_size and the period_size, because the latter is assumed by the runtime->hw_ptr_interrupt calculation. However, due to the lack of a ioctl that could read the software parameters before they are set, the kernel requires that alsa-lib calculates the boundary value, too. The changed algorithm leads to a different boundary value used by alsa-lib, which makes, e.g., mplayer fail to play a 44.1 kHz file because the silence_size parameter is now invalid; bug report: <https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5015>. This patch reverts the change to the boundary calculation, and instead fixes the hw_ptr_interrupt calculation to be period-aligned regardless of the boundary value. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-03-26ALSA: pcm_lib - fix xrun functionalityJarkko Nikula
The commit 4d96eb255c53ab5e39b37fd4d484ea3dc39ab456 broke the interrupt time xrun functionality (stream stop etc.) if the CONFIG_SND_PCM_XRUN_DEBUG is not set. This is because the xrun() is null defined without it. Fix this by letting the function xrun() to be always defined as it was before. Signed-off-by: Jarkko Nikula <jhnikula@gmail.com> Cc: Jaroslav Kysela <perex@perex.cz> Signed-off-by: Takashi Iwai <tiwai@suse.de>
2010-01-26Merge remote branch 'alsa/devel' into topic/miscTakashi Iwai
2010-01-26ALSA: pcm_lib - return back hw_ptr_interruptJaroslav Kysela
Clemens Ladisch noted for hw_ptr_removal in "cleanup & merge hw_ptr update functions" commit: "It is possible for the status/delay ioctls to be called when the sound card's pointer register alreay shows a position at the beginning of the new period, but immediately before the interrupt is actually executed. (This happens regularly on a SMP machine with mplayer.) When that happens, the code thinks that the position must be at least one period ahead of the current position and drops an entire buffer of data." Return back the hw_ptr_interrupt variable. The last interrupt pointer is always computed from the latest hw_ptr instead of tracking it separately (in this case all hw_ptr checks and modifications might influence also hw_ptr_interrupt and it is difficult to keep it consistent). Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-21Merge remote branch 'alsa/devel' into topic/miscTakashi Iwai
2010-01-21ALSA: pcm_core: Fix wake_up() optimizationJaroslav Kysela
This change fixes the "ALSA: pcm_lib - optimize wake_up() calls for PCM I/O" commit. New sleeping queue is introduced to separate user space and kernel space wake_ups. runtime->nowake is renamed to twake (transfer wake). Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-13Merge branch 'devel' of git.alsa-project.org:alsa-kernel into topic/miscTakashi Iwai
2010-01-13ALSA: pcm_lib - fix wrong delta print for jiffies checkJaroslav Kysela
The previous jiffies delta was 0 in all cases. Use hw_ptr variable to store and print original value. Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-12Merge commit alsa/devel into topic/miscTakashi Iwai
Conflicts: include/sound/version.h
2010-01-08Merge branch 'topic/hda' of ↵Jaroslav Kysela
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 into devel
2010-01-08ALSA: pcm_lib: fix "something must be really wrong" conditionJaroslav Kysela
When runtime->periods == 1 or when pointer crosses end of ring buffer, the delta might be greater than buffer_size. Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-07ALSA: pcm_lib - optimize wake_up() calls for PCM I/OJaroslav Kysela
As noted by pl bossart <bossart.nospam@gmail.com>, the PCM I/O routines (snd_pcm_lib_write1, snd_pcm_lib_read1) should block wake_up() calls until all samples are not processed. Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-07ALSA: pcm_lib - cleanup & merge hw_ptr update functionsJaroslav Kysela
Do general cleanup in snd_pcm_update_hw_ptr*() routines and merge them. The main change is hw_ptr_interrupt variable removal to simplify code logic. This variable can be computed directly from hw_ptr. Ensure that updated hw_ptr is not lower than previous one (it was possible with old code in some obscure situations when interrupt was delayed or the lowlevel driver returns wrong ring buffer position value). Signed-off-by: Jaroslav Kysela <perex@perex.cz>
2010-01-07ALSA: pcm_lib - add possibility to log last 10 DMA ring buffer positionsJaroslav Kysela
In some debug cases, it might be usefull to see previous ring buffer positions to determine position problems from the lowlevel drivers. Signed-off-by: Jaroslav Kysela <perex@perex.cz>