The current compress offload timestamping API relies on struct
snd_compr_tstamp, whose cumulative counters like copied_total are
defined as __u32. On long-running high-resolution audio streams, these
32-bit counters can overflow, causing incorrect availability
calculations.

This patch series transitions to a 64-bit safe API to solve the problem
while maintaining perfect backward compatibility with the existing UAPI.
The pointer operation is reworked to use a new timestamp struct with
64-bit fields for the cumulative counters, named snd_compr_tstamp64.
ASoC drivers are updated to use the 64-bit structures. Corresponding
ioctls are added to expose them to user-space.

The series is structured as follows:

Patch 1: Updates the pointer op, refactors the core logic and ASoC
drivers to use it, and defines the new UAPI structs.

Patch 2: Exposes the SNDRV_COMPRESS_TSTAMP64 ioctl.

Patch 3: Exposes the corresponding SNDRV_COMPRESS_AVAIL64 ioctl.

This series has been tested on a Pixel 9 device. All compress offload
use cases, including long-running playback, were verified to work
correctly with the new 64-bit API.

Thanks,
Joris (George) Verhaegen

Signed-off-by: Joris Verhaegen <verhaegen@google.com>

---
Changes in v2:
  - Corrected author and Signed-off-by to be consistent (Mark Brown).
Changes in v3:
  - Rework pointer op to return 64-bit timestamp, rather than adding a
    parallel pointer64 op (Charles Keepax, Takashi Iwai, Vinod Koul)
  - Bump the protocol version for ABI change (Takashi Iwai)
  -Fix linker error on Intel Atom (lkp@intel.com)
  -Rebase on latest for-next sound tree (Takashi Iwai)
  -Avoid changing return error code for ioctl (internal)
  -ASoC: Replace u64 % u32 by do_div(u64, u32) (internal)
  -ASoC: sprd: change current_data_offset to u64 (internal)

Joris Verhaegen (3):
  ALSA: compress_offload: Add 64-bit safe timestamp infrastructure
  ALSA: compress_offload: Add SNDRV_COMPRESS_TSTAMP64 ioctl
  ALSA: compress_offload: Add SNDRV_COMPRESS_AVAIL64 ioctl

 include/sound/compress_driver.h               |   2 +-
 include/sound/soc-component.h                 |   4 +-
 include/sound/soc-dai.h                       |   7 +-
 include/uapi/sound/compress_offload.h         |  35 +++++-
 sound/core/compress_offload.c                 | 100 ++++++++++++------
 sound/soc/codecs/wm_adsp.c                    |   4 +-
 sound/soc/codecs/wm_adsp.h                    |   2 +-
 .../intel/atom/sst-mfld-platform-compress.c   |  12 ++-
 sound/soc/intel/atom/sst-mfld-platform.h      |   2 +-
 sound/soc/intel/atom/sst/sst_drv_interface.c  |   9 +-
 sound/soc/qcom/qdsp6/q6apm-dai.c              |  26 +++--
 sound/soc/qcom/qdsp6/q6asm-dai.c              |  26 +++--
 sound/soc/soc-component.c                     |   2 +-
 sound/soc/soc-compress.c                      |   2 +-
 sound/soc/soc-dai.c                           |   2 +-
 sound/soc/sof/compress.c                      |   2 +-
 sound/soc/sprd/sprd-pcm-compress.c            |   6 +-
 sound/soc/sprd/sprd-pcm-dma.h                 |   4 +-
 sound/soc/uniphier/aio-compress.c             |   2 +-
 19 files changed, 167 insertions(+), 82 deletions(-)

-- 
2.50.1.470.g6ba607880d-goog

On Fri, 25 Jul 2025 13:42:42 +0200,
Joris Verhaegen wrote:
> 
> The current compress offload timestamping API relies on struct
> snd_compr_tstamp, whose cumulative counters like copied_total are
> defined as __u32. On long-running high-resolution audio streams, these
> 32-bit counters can overflow, causing incorrect availability
> calculations.
> 
> This patch series transitions to a 64-bit safe API to solve the problem
> while maintaining perfect backward compatibility with the existing UAPI.
> The pointer operation is reworked to use a new timestamp struct with
> 64-bit fields for the cumulative counters, named snd_compr_tstamp64.
> ASoC drivers are updated to use the 64-bit structures. Corresponding
> ioctls are added to expose them to user-space.
> 
> The series is structured as follows:
> 
> Patch 1: Updates the pointer op, refactors the core logic and ASoC
> drivers to use it, and defines the new UAPI structs.
> 
> Patch 2: Exposes the SNDRV_COMPRESS_TSTAMP64 ioctl.
> 
> Patch 3: Exposes the corresponding SNDRV_COMPRESS_AVAIL64 ioctl.
> 
> This series has been tested on a Pixel 9 device. All compress offload
> use cases, including long-running playback, were verified to work
> correctly with the new 64-bit API.
> 
> Thanks,
> Joris (George) Verhaegen
> 
> Signed-off-by: Joris Verhaegen <verhaegen@google.com>

Through a quick glance, the patches look OK, but since it's too late
for 6.17 merge window for such a non-trivial core API change, so I'll
postpone the merge for 6.18.


thanks,

Takashi

On Fri, Jul 25, 2025 at 12:42:42PM +0100, Joris Verhaegen wrote:
> The current compress offload timestamping API relies on struct
> snd_compr_tstamp, whose cumulative counters like copied_total are
> defined as __u32. On long-running high-resolution audio streams, these
> 32-bit counters can overflow, causing incorrect availability
> calculations.

Acked-by: Mark Brown <broonie@kernel.org>