linux-kernel - Re: [PATCH v3 0/3] ALSA: compress_offload: Add 64-bit safe timestamp API

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Message-ID: <87cy9oidg8.wl-tiwai@suse.de>
Date: Fri, 25 Jul 2025 15:53:43 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Joris Verhaegen <verhaegen@...gle.com>
Cc: Vinod Koul <vkoul@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Cezary Rojewski <cezary.rojewski@...el.com>,
	Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
	Bard Liao <yung-chuan.liao@...ux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
	Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
	Pierre-Louis Bossart <pierre-louis.bossart@...ux.dev>,
	Srinivas Kandagatla <srini@...nel.org>,
	Daniel Baluta <daniel.baluta@....com>,
	Orson Zhai <orsonzhai@...il.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Chunyan Zhang <zhang.lyra@...il.com>,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	kernel-team@...roid.com,
	linux-sound@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	patches@...nsource.cirrus.com,
	linux-arm-msm@...r.kernel.org,
	sound-open-firmware@...a-project.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/3] ALSA: compress_offload: Add 64-bit safe timestamp API

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@...gle.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