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ALSA: hda - hdmi: Skip out-of-range latency values in AMD ELD generator

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The ATI/AMD video/audio latencies are specified in apparent HDMI VSDB
format. In this format values above 251 are not valid (or stream
component is not supported - 255), but no checking is performed since
this was not mentioned in the AMD HDA verbs specification.

Check that the latencies are valid before using them, and add a comment
describing the formats.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Anssi Hannula 2013-11-10 20:56:11 +02:00 committed by Takashi Iwai
parent 13122e6ebf
commit a5666824ce
1 changed files with 19 additions and 4 deletions
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23
sound/pci/hda/hda_eld.c
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@ -768,13 +768,28 @@ int snd_hdmi_get_eld_ati(struct hda_codec *codec, hda_nid_t nid,
return -EINVAL;
}
/*
* HDMI VSDB latency format:
* separately for both audio and video:
* 0 field not valid or unknown latency
* [1..251] msecs = (x-1)*2 (max 500ms with x = 251 = 0xfb)
* 255 audio/video not supported
*
* HDA latency format:
* single value indicating video latency relative to audio:
* 0 unknown or 0ms
* [1..250] msecs = x*2 (max 500ms with x = 250 = 0xfa)
* [251..255] reserved
*/
aud_synch = snd_hda_codec_read(codec, nid, 0, ATI_VERB_GET_AUDIO_VIDEO_DELAY, 0);
if ((aud_synch & ATI_DELAY_VIDEO_LATENCY) && (aud_synch & ATI_DELAY_AUDIO_LATENCY)) {
int video_latency = (aud_synch & ATI_DELAY_VIDEO_LATENCY) - 1;
int audio_latency = ((aud_synch & ATI_DELAY_AUDIO_LATENCY) >> 8) - 1;
int video_latency_hdmi = (aud_synch & ATI_DELAY_VIDEO_LATENCY);
int audio_latency_hdmi = (aud_synch & ATI_DELAY_AUDIO_LATENCY) >> 8;
if (video_latency > audio_latency)
buf[6] = min(video_latency - audio_latency, 0xfa);
if (video_latency_hdmi <= 0xfb && audio_latency_hdmi <= 0xfb &&
video_latency_hdmi > audio_latency_hdmi)
buf[6] = video_latency_hdmi - audio_latency_hdmi;
/* else unknown/invalid or 0ms or video ahead of audio, so use zero */
}
/* Baseline length */