[alsa-devel] [PATCH v5 06/10] ALSA: core: pass audio tstamp config from userspace

[Takashi Iwai]

At Fri,  6 Feb 2015 15:55:55 -0600,
Pierre-Louis Bossart wrote:
> 
> Let userspace select audio timestamp config when the
> STATUS_EXT ioctl is used, ignore and zero all
> other fields
> No change for the existing STATUS ioctl, parameters
> are treated as read-only.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
>  sound/core/pcm_native.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index d50f3e6..40d2943 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -753,12 +753,27 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
>  }
>  
>  static int snd_pcm_status_user(struct snd_pcm_substream *substream,
> -			       struct snd_pcm_status __user * _status)
> +			       struct snd_pcm_status __user * _status,
> +			       bool ext)
>  {
>  	struct snd_pcm_status status;
>  	int res;
> -	
> -	memset(&status, 0, sizeof(status));
> +	u32  audio_tstamp_data;
> +	u32  __user *_audio_tstamp_data;
> +
> +	if (ext == false) {
> +		memset(&status, 0, sizeof(status));
> +	} else {
> +		/*
> +		 * parameters are read/write, get audio_tstamp_data from user,
> +		 * ignore rest of status structure
> +		 */
> +		_audio_tstamp_data = (u32 __user *)(&_status->audio_tstamp_data);
> +		if (get_user(audio_tstamp_data, _audio_tstamp_data))
> +			return -EFAULT;
> +		memset(&status, 0, sizeof(status));
> +		status.audio_tstamp_data = audio_tstamp_data;
> +	}

It can be simplified a bit, e.g.

	memset(&status, 0, sizeof(status));
	if (ext &&
	    get_user(status.audio_tstamp_data, &_status->audio_tstamp_data))
		return -EFAULT;


Takashi