Re: [alsa-devel] [PATCH v2] ALSA: hda - Update chmap tlv to report sink's capability

On Fri, Apr 01, 2016 at 02:26:32PM +0200, Takashi Iwai wrote:

On Fri, 01 Apr 2016 12:18:51 +0200, Subhransu S. Prusty wrote:

...

• 	dst += 2;
  

• 	size -= 8;
  

• 	count += 8;
  

• 	if (size < chs_bytes)
  

• 		return -ENOMEM;
  

• 	size -= chs_bytes;
  

• 	count += chs_bytes;
  

• 	chmap->ops.cea_alloc_to_tlv_chmap(chmap, cap,
  

• 				tlv_chmap, chs);
  

• 	if (copy_to_user(dst, tlv_chmap, chs_bytes))
  

• 		return -EFAULT;
  

• 	dst += chs;
  

• }
  

• }

• if (size < 8)

• return -ENOMEM;
  

• spk_alloc = chmap->ops.get_spk_alloc(chmap->hdac, pcm_idx);
• cap = get_cap_from_spk_alloc(spk_alloc);
• chs = cap->channels;
• chs_bytes = chs * 4;
• type = chmap->ops.chmap_cea_alloc_validate_get_type(chmap, cap, chs);
• if (type < 0)

• return -ENODEV;
  

• if (put_user(type, dst) ||

•    put_user(chs_bytes, dst + 1))
  

• return -EFAULT;
  

• dst += 2;
• size -= 8;
• count += 8;
• if (size < chs_bytes)

• return -ENOMEM;
  

• count += chs_bytes;
• chmap->ops.cea_alloc_to_tlv_chmap(chmap, cap, tlv_chmap, chs);
• if (copy_to_user(dst, tlv_chmap, chs_bytes))

• return -EFAULT;
  

• if (put_user(count, tlv + 1)) return -EFAULT;
• return 0;

So, this change means that TLV returns only a single channel map corresponding to the given speaker bits? This doesn't sound right. TLV should return the all possible channel maps the device are capable of. A device with four channels can drive also two channels streams, too, for example.

Hi Takashi,

The device does report only the speaker allocation i.e. only the channels it support. So I think it is good to return only a single channel map that best matches the device's capability. As the device reports the channels it is capable of, user should be able to set any number of channels in any order looking at this map.

Please let me know if you are ok with this. Otherwise, I will change to what you suggest.

Regards, Subhransu

Takashi

--