[alsa-devel] [PATCH] ALSA: core: fix 64-bit SNDRV_PCM_IOCTL_STATUS ABI breakage

[Takashi Iwai]

At Sat, 27 Oct 2012 21:55:27 +0200,
Clemens Ladisch wrote:
> 
> Commit 4eeaaeaea (ALSA: core: add hooks for audio timestamps) added the
> new audio_tstamp field to struct snd_pcm_status.  However, struct
> timespec requires 64-bit alignment, so the 64-bit compiler would insert
> 32 bits of padding before this field, which broke SNDRV_PCM_IOCTL_STATUS
> with error messages like this:
> 
>   kernel: unknown ioctl = 0x80984120
> 
> To solve this, insert the padding explicitly so that it can be taken
> into account when calculating the ABI structure size.
> 
> Signed-off-by: Clemens Ladisch <clemens at ladisch.de>

Oops, that's bad.  Thanks for catching this.
I applied it now to for-next branch.

Could you fix alsa-lib code as well?


Takashi


> ---
>  include/uapi/sound/asound.h |    3 ++-
>  sound/core/pcm_compat.c     |    3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> --- a/include/uapi/sound/asound.h
> +++ b/include/uapi/sound/asound.h
> @@ -408,8 +408,9 @@ struct snd_pcm_status {
>  	snd_pcm_uframes_t avail_max;	/* max frames available on hw since last status */
>  	snd_pcm_uframes_t overrange;	/* count of ADC (capture) overrange detections from last status */
>  	snd_pcm_state_t suspended_state; /* suspended stream state */
> +	__u32 reserved_alignment;	/* must be filled with zero */
>  	struct timespec audio_tstamp;	/* from sample counter or wall clock */
> -	unsigned char reserved[60-sizeof(struct timespec)]; /* must be filled with zero */
> +	unsigned char reserved[56-sizeof(struct timespec)]; /* must be filled with zero */
>  };
> 
>  struct snd_pcm_mmap_status {
> --- a/sound/core/pcm_compat.c
> +++ b/sound/core/pcm_compat.c
> @@ -190,8 +190,9 @@ struct snd_pcm_status32 {
>  	u32 avail_max;
>  	u32 overrange;
>  	s32 suspended_state;
> +	u32 reserved_alignment;
>  	struct compat_timespec audio_tstamp;
> -	unsigned char reserved[60-sizeof(struct compat_timespec)];
> +	unsigned char reserved[56-sizeof(struct compat_timespec)];
>  } __attribute__((packed));
> 
>