Re: OSS SNDCTL_DSP_GETISPACE, non-blocking read: messy :-\

[Takashi Iwai <tiwai@suse.de>]

At Tue, 28 Oct 2003 14:30:33 +0100 (CET),
Jaroslav wrote:
> 
> Yes, several assumptions were made and the SPACE ioctls were a bit broken.
> I've put a fix to our CVS (also included to this e-mail). Hopefully, it
> won't break another OSS applications.
> 
> 						Jaroslav
> 
> Index: pcm_oss.c
> ===================================================================
> RCS file: /cvsroot/alsa/alsa-kernel/core/oss/pcm_oss.c,v
> retrieving revision 1.53
> diff -u -r1.53 pcm_oss.c
> --- pcm_oss.c	30 Sep 2003 09:28:26 -0000	1.53
> +++ pcm_oss.c	28 Oct 2003 13:26:12 -0000
> @@ -125,8 +125,8 @@
>  	if (runtime->period_size == runtime->oss.period_bytes)
>  		return frames;
>  	if (runtime->period_size < runtime->oss.period_bytes)
> -		return frames * (runtime->oss.period_bytes / runtime->period_size);
> -	return frames / (runtime->period_size / runtime->oss.period_bytes);
> +		return (frames * runtime->period_size) / runtime->oss.period_bytes;
> +	return (frames * runtime->oss.period_bytes) / runtime->period_size;
>  }

oh yeah, this is...


>  static int snd_pcm_oss_format_from(int format)
> @@ -451,7 +451,7 @@
>  	sw_params->tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
>  	sw_params->period_step = 1;
>  	sw_params->sleep_min = 0;
> -	sw_params->avail_min = runtime->period_size;
> +	sw_params->avail_min = 1;
>  	sw_params->xfer_align = 1;
>  	if (atomic_read(&runtime->mmap_count) ||
>  	    (substream->oss.setup && substream->oss.setup->nosilence)) {
> @@ -470,7 +470,6 @@
>  		snd_printd("SW_PARAMS failed: %i\n", err);
>  		goto failure;
>  	}
> -	runtime->control->avail_min = runtime->period_size;
> 
>  	runtime->oss.periods = params_periods(sparams);
>  	oss_period_size = snd_pcm_plug_client_size(substream, params_period_size(sparams));
> @@ -883,7 +882,7 @@
>  				if (tmp <= 0)
>  					return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp;
>  				runtime->oss.bytes += tmp;
> -				runtime->oss.buffer_used = runtime->oss.period_bytes;
> +				runtime->oss.buffer_used = tmp;
>  			}
>  			tmp = bytes;
>  			if ((size_t) tmp > runtime->oss.buffer_used)
> @@ -1425,6 +1424,7 @@

i think the read size should be changed, too.

				tmp = snd_pcm_oss_read2(substream, runtime->oss.buffer, runtime->oss.period_bytes, 1);

also, the line below

			if (copy_to_user(buf, runtime->oss.buffer + (runtime->oss.period_bytes - runtime->oss.buffer_used), tmp))

the offset calculation is broken if you use buffer_used = tmp.
we'll need another field like my patch to calculate the current
offset.


Takashi


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