Re: [PATCH v4 2/3] ALSA: compress_offload: Add SNDRV_COMPRESS_TSTAMP64 ioctl

[Vinod Koul <vkoul@kernel.org>]

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

> +		ret = copy_to_user((void __user *)arg, copy_from, copy_size) ?
>  			      -EFAULT :
>  			      0;
>  	}
> @@ -1327,7 +1332,9 @@ static long snd_compr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
>  
>  	switch (cmd) {
>  	case SNDRV_COMPRESS_TSTAMP:
> -		return snd_compr_tstamp(stream, arg);
> +		return snd_compr_tstamp(stream, arg, true);
> +	case SNDRV_COMPRESS_TSTAMP64:
> +		return snd_compr_tstamp(stream, arg, false);
>  	case SNDRV_COMPRESS_AVAIL:
>  		return snd_compr_ioctl_avail(stream, arg);
>  	case SNDRV_COMPRESS_PAUSE:
> -- 
> 2.50.1.565.gc32cd1483b-goog

-- 
~Vinod