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Message-ID: <87h5ym1f75.wl-tiwai@suse.de>
Date: Tue, 05 Aug 2025 07:59:42 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Vinod Koul <vkoul@...nel.org>
Cc: Joris Verhaegen <verhaegen@...gle.com>,
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,
Miller Liang <millerliang@...gle.com>
Subject: Re: [PATCH v4 2/3] ALSA: compress_offload: Add SNDRV_COMPRESS_TSTAMP64 ioctl
On Tue, 05 Aug 2025 06:47:59 +0200,
Vinod Koul wrote:
>
> On 01-08-25, 10:27, Joris Verhaegen wrote:
> > The previous patch introduced the internal infrastructure for handling
> > 64-bit timestamps. This patch exposes this capability to user-space.
> >
> > Define the new ioctl command SNDRV_COMPRESS_TSTAMP64, which allows
> > applications to fetch the overflow-safe struct snd_compr_tstamp64.
> >
> > The ioctl dispatch table is updated to handle the new command by
> > calling a new snd_compr_tstamp64 handler, while the legacy path is
> > renamed to snd_compr_tstamp32 for clarity.
> >
> > This patch bumps the SNDRV_COMPRESS_VERSION to 0.4.0.
> >
> > Reviewed-by: Miller Liang <millerliang@...gle.com>
> > Tested-by: Joris Verhaegen <verhaegen@...gle.com>
> > Signed-off-by: Joris Verhaegen <verhaegen@...gle.com>
> > ---
> > include/uapi/sound/compress_offload.h | 5 +++--
> > sound/core/compress_offload.c | 19 +++++++++++++------
> > 2 files changed, 16 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/uapi/sound/compress_offload.h b/include/uapi/sound/compress_offload.h
> > index abd0ea3f86ee..70b8921601f9 100644
> > --- a/include/uapi/sound/compress_offload.h
> > +++ b/include/uapi/sound/compress_offload.h
> > @@ -13,8 +13,7 @@
> > #include <sound/asound.h>
> > #include <sound/compress_params.h>
> >
> > -
> > -#define SNDRV_COMPRESS_VERSION SNDRV_PROTOCOL_VERSION(0, 3, 0)
> > +#define SNDRV_COMPRESS_VERSION SNDRV_PROTOCOL_VERSION(0, 4, 0)
> > /**
> > * struct snd_compressed_buffer - compressed buffer
> > * @fragment_size: size of buffer fragment in bytes
> > @@ -208,6 +207,7 @@ struct snd_compr_task_status {
> > * Note: only codec params can be changed runtime and stream params cant be
> > * SNDRV_COMPRESS_GET_PARAMS: Query codec params
> > * SNDRV_COMPRESS_TSTAMP: get the current timestamp value
> > + * SNDRV_COMPRESS_TSTAMP64: get the current timestamp value in 64 bit format
> > * SNDRV_COMPRESS_AVAIL: get the current buffer avail value.
> > * This also queries the tstamp properties
> > * SNDRV_COMPRESS_PAUSE: Pause the running stream
> > @@ -230,6 +230,7 @@ struct snd_compr_task_status {
> > struct snd_compr_metadata)
> > #define SNDRV_COMPRESS_TSTAMP _IOR('C', 0x20, struct snd_compr_tstamp)
> > #define SNDRV_COMPRESS_AVAIL _IOR('C', 0x21, struct snd_compr_avail)
> > +#define SNDRV_COMPRESS_TSTAMP64 _IOR('C', 0x22, struct snd_compr_tstamp64)
> > #define SNDRV_COMPRESS_PAUSE _IO('C', 0x30)
> > #define SNDRV_COMPRESS_RESUME _IO('C', 0x31)
> > #define SNDRV_COMPRESS_START _IO('C', 0x32)
> > diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> > index d3164aa07158..445220fdb6a0 100644
> > --- a/sound/core/compress_offload.c
> > +++ b/sound/core/compress_offload.c
> > @@ -736,18 +736,23 @@ snd_compr_set_metadata(struct snd_compr_stream *stream, unsigned long arg)
> > return retval;
> > }
> >
> > -static inline int
> > -snd_compr_tstamp(struct snd_compr_stream *stream, unsigned long arg)
> > +static inline int snd_compr_tstamp(struct snd_compr_stream *stream,
> > + unsigned long arg, bool is_32bit)
> > {
> > struct snd_compr_tstamp64 tstamp64 = { 0 };
> > struct snd_compr_tstamp tstamp32 = { 0 };
> > + const void *copy_from = &tstamp64;
> > + size_t copy_size = sizeof(tstamp64);
> > int ret;
> >
> > ret = snd_compr_update_tstamp(stream, &tstamp64);
> > if (ret == 0) {
> > - snd_compr_tstamp32_from_64(&tstamp32, &tstamp64);
> > - ret = copy_to_user((struct snd_compr_tstamp __user *)arg,
> > - &tstamp32, sizeof(tstamp32)) ?
> > + if (is_32bit) {
> > + snd_compr_tstamp32_from_64(&tstamp32, &tstamp64);
> > + copy_from = &tstamp32;
> > + copy_size = sizeof(tstamp32);
> > + }
>
> Most of the applications and people would be 32bit right now and we
> expect this to progressively change, but then this imposes a penalty as
> default path is 64 bit, since we expect this ioctl to be called very
> frequently, should we do this optimization for 64bit here?
Through a quick glance over the patch, I don't think you'll hit the
significant performance loss. It's merely a few bytes of extra copies
before copy_to_user(), after all. But, of course, it'd be more
convincing if anyone can test and give the actual numbers.
thanks,
Takashi
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