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

[Takashi Iwai]

On Fri, 01 Apr 2016 12:18:51 +0200,
Subhransu S. Prusty wrote:
> 
> The existing TLV callback implementation copies all of the
> cea_channel_speaker_allocation map table to the TLV container
> irrespective of what is reported by sink. This is of little use
> to the userspace application.
> 
> With this patch, it parses the spk_alloc block as queried from
> the ELD, and copies only the corresponding channel map from the
> cea channel speaker allocation table. Thus the user can parse the
> TLV container to identify sink's capability and set the channel
> map accordingly.
> 
> It shouldn't impact the behavior in AMD chipset, as this makes
> use of already parsed spk alloc block to calculate the channel
> map.
> 
> Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty at intel.com>
> Signed-off-by: Vinod Koul <vinod.koul at intel.com>
> ---
> 
> changes in v2:
> 	Updated the commit message to make it more understandable.

Thanks, I'm now rereading the patch after realizing what's doing.
So some questions:

>  include/sound/hda_chmap.h  |  2 ++
>  sound/hda/hdmi_chmap.c     | 90 +++++++++++++++++++++++++++++-----------------
>  sound/pci/hda/patch_hdmi.c | 13 +++++++
>  3 files changed, 72 insertions(+), 33 deletions(-)
> 
> diff --git a/include/sound/hda_chmap.h b/include/sound/hda_chmap.h
> index e20d219..babd445 100644
> --- a/include/sound/hda_chmap.h
> +++ b/include/sound/hda_chmap.h
> @@ -36,6 +36,8 @@ struct hdac_chmap_ops {
>  	int (*chmap_validate)(struct hdac_chmap *hchmap, int ca,
>  			int channels, unsigned char *chmap);
>  
> +	int (*get_spk_alloc)(struct hdac_device *hdac, int pcm_idx);
> +
>  	void (*get_chmap)(struct hdac_device *hdac, int pcm_idx,
>  					unsigned char *chmap);
>  	void (*set_chmap)(struct hdac_device *hdac, int pcm_idx,
> diff --git a/sound/hda/hdmi_chmap.c b/sound/hda/hdmi_chmap.c
> index d7ec862..9406203 100644
> --- a/sound/hda/hdmi_chmap.c
> +++ b/sound/hda/hdmi_chmap.c
> @@ -625,13 +625,40 @@ static void hdmi_cea_alloc_to_tlv_chmap(struct hdac_chmap *hchmap,
>  	WARN_ON(count != channels);
>  }
>  
> +static struct hdac_cea_channel_speaker_allocation *get_cap_from_spk_alloc(
> +							int spk_alloc)
> +{
> +	int i, spk_mask = 0;
> +
> +	if (!spk_alloc)
> +		return &channel_allocations[0];
> +
> +	for (i = 0; i < ARRAY_SIZE(eld_speaker_allocation_bits); i++) {
> +		if (spk_alloc & (1 << i))
> +			spk_mask |= eld_speaker_allocation_bits[i];
> +	}
> +
> +	/* Get num channels using spk mask */
> +	for (i = 0; i < ARRAY_SIZE(channel_allocations); i++) {
> +		if ((spk_mask & channel_allocations[i].spk_mask) == spk_mask)
> +			return &channel_allocations[i];
> +	}
> +
> +	return &channel_allocations[0];
> +}

This function returns the channel allocation corresponding to the
given speakers, right?  Don't you need to pass the number of channels?
(The question is relevant with below.)


>  static int hdmi_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
>  			      unsigned int size, unsigned int __user *tlv)
>  {
>  	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
>  	struct hdac_chmap *chmap = info->private_data;
> +	int pcm_idx = kcontrol->private_value;
>  	unsigned int __user *dst;
> -	int chs, count = 0;
> +	int chs, count = 0, chs_bytes;
> +	int type;
> +	unsigned int tlv_chmap[8];
> +	int spk_alloc;
> +	struct hdac_cea_channel_speaker_allocation *cap;
>  
>  	if (size < 8)
>  		return -ENOMEM;
> @@ -639,40 +666,37 @@ static int hdmi_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
>  		return -EFAULT;
>  	size -= 8;
>  	dst = tlv + 2;
> -	for (chs = 2; chs <= chmap->channels_max; chs++) {
> -		int i;
> -		struct hdac_cea_channel_speaker_allocation *cap;
> -
> -		cap = channel_allocations;
> -		for (i = 0; i < ARRAY_SIZE(channel_allocations); i++, cap++) {
> -			int chs_bytes = chs * 4;
> -			int type = chmap->ops.chmap_cea_alloc_validate_get_type(
> -								chmap, cap, chs);
> -			unsigned int tlv_chmap[8];
> -
> -			if (type < 0)
> -				continue;
> -			if (size < 8)
> -				return -ENOMEM;
> -			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;
> -			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.


Takashi