[alsa-devel] [PATCH v4 1/9] ALSA: hda/hdmi - implement mst_no_extra_pcms flag

[Takashi Iwai]

On Thu, 12 Sep 2019 16:21:52 +0200,
Kai Vehmanen wrote:
> 
> To support the DP-MST multiple streams via single connector feature,
> the HDMI driver was extended with the concept of backup PCMs. See
> commit 9152085defb6 ("ALSA: hda - add DP MST audio support").
> 
> This implementation works fine with snd_hda_intel.c as PCM topology
> is fully managed within the single driver.
> 
> When the HDA codec driver is used from ASoC components, the concept
> of backup PCMs no longer fits. For ASoC topologies, the physical
> HDMI converters are presented as backend DAIs and these should match
> with hardware capabilities. The ASoC topology may define arbitrary
> PCMs (i.e. frontend DAIs) and have processing elements before eventual
> routing to the HDMI BE DAIs. With backup PCMs, the link between
> FE and BE DAIs would become dynamic and change when monitors are
> (un)plugged. This would lead to modifying the topology every time
> hotplug events happen, which is not currently possible in ASoC and
> there does not seem to be any obvious benefits from this design.
> 
> To overcome above problems and enable the HDMI driver to be used
> from ASoC, this patch adds a new mode (mst_no_extra_pcms flags) to
> patch_hdmi.c. In this mode, the codec driver does not assume
> the backup PCMs to be created.
> 
> Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>

Looks good to me.
Reviewed-by: Takashi Iwai <tiwai at suse.de>


thanks,

Takashi


> ---
>  include/sound/hda_codec.h  |  1 +
>  sound/pci/hda/patch_hdmi.c | 19 ++++++++++++++-----
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/include/sound/hda_codec.h b/include/sound/hda_codec.h
> index 9a0393cf024c..ac18f428eda6 100644
> --- a/include/sound/hda_codec.h
> +++ b/include/sound/hda_codec.h
> @@ -254,6 +254,7 @@ struct hda_codec {
>  	unsigned int force_pin_prefix:1; /* Add location prefix */
>  	unsigned int link_down_at_suspend:1; /* link down at runtime suspend */
>  	unsigned int relaxed_resume:1;	/* don't resume forcibly for jack */
> +	unsigned int mst_no_extra_pcms:1; /* no backup PCMs for DP-MST */
>  
>  #ifdef CONFIG_PM
>  	unsigned long power_on_acct;
> diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
> index bca5de78e9ad..59aaee4a40fd 100644
> --- a/sound/pci/hda/patch_hdmi.c
> +++ b/sound/pci/hda/patch_hdmi.c
> @@ -2072,15 +2072,24 @@ static bool is_hdmi_pcm_attached(struct hdac_device *hdac, int pcm_idx)
>  static int generic_hdmi_build_pcms(struct hda_codec *codec)
>  {
>  	struct hdmi_spec *spec = codec->spec;
> -	int idx;
> +	int idx, pcm_num;
>  
>  	/*
>  	 * for non-mst mode, pcm number is the same as before
> -	 * for DP MST mode, pcm number is (nid number + dev_num - 1)
> -	 *  dev_num is the device entry number in a pin
> -	 *
> +	 * for DP MST mode without extra PCM, pcm number is same
> +	 * for DP MST mode with extra PCMs, pcm number is
> +	 *  (nid number + dev_num - 1)
> +	 * dev_num is the device entry number in a pin
>  	 */
> -	for (idx = 0; idx < spec->num_nids + spec->dev_num - 1; idx++) {
> +
> +	if (codec->mst_no_extra_pcms)
> +		pcm_num = spec->num_nids;
> +	else
> +		pcm_num = spec->num_nids + spec->dev_num - 1;
> +
> +	codec_dbg(codec, "hdmi: pcm_num set to %d\n", pcm_num);
> +
> +	for (idx = 0; idx < pcm_num; idx++) {
>  		struct hda_pcm *info;
>  		struct hda_pcm_stream *pstr;
>  
> -- 
> 2.17.1
> 
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