[alsa-devel] [PATCH 2/2] ALSA: hda - Bind with i915 only when Intel graphics is present

[Ville Syrjälä]

On Wed, Mar 30, 2016 at 05:46:02PM +0200, Takashi Iwai wrote:
> On Skylake and onwards, the HD-audio controller driver needs to bind
> with i915 for having the control of power well audio domain before
> actually probing the codec.  This leads to the load of i915 driver
> from the audio driver side.  But, there are systems that have no Intel
> graphics but Nvidia or AMD GPU, although they still use HD-audio bus
> for the onboard audio codecs.  On these, loading the i915 driver is
> nothing but a useless memory and CPU consumption.
> 
> A simple way to avoid it is just to look for the Intel graphics PCI
> entry beforehand, and try to bind with i915 only when such an entry is
> found.  Currently, it assumes the PCI display class.  If another class
> appears, this needs to be extended (although it's very unlikely).
> 
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>  sound/hda/hdac_i915.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
> index c62a9f830b84..3c8e6d93d4df 100644
> --- a/sound/hda/hdac_i915.c
> +++ b/sound/hda/hdac_i915.c
> @@ -298,6 +298,17 @@ int snd_hdac_i915_register_notifier(const struct i915_audio_component_audio_ops
>  }
>  EXPORT_SYMBOL_GPL(snd_hdac_i915_register_notifier);
>  
> +/* check whether intel graphics is present */
> +static bool i915_gfx_present(void)
> +{
> +	static struct pci_device_id ids[] = {
> +		{ PCI_DEVICE_CLASS(PCI_BASE_CLASS_DISPLAY << 16, 0xff0000) },
> +		{}
> +	};
> +	return pci_dev_present(ids);
> +}

Should this be checking for at least the Intel vendor ID? External GPUs
should be display class devices too, no?

> +
> +
>  /**
>   * snd_hdac_i915_init - Initialize i915 audio component
>   * @bus: HDA core bus
> @@ -320,6 +331,9 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
>  	if (WARN_ON(hdac_acomp))
>  		return -EBUSY;
>  
> +	if (!i915_gfx_present())
> +		return -ENODEV;
> +
>  	acomp = kzalloc(sizeof(*acomp), GFP_KERNEL);
>  	if (!acomp)
>  		return -ENOMEM;
> -- 
> 2.7.4
> 
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-- 
Ville Syrjälä
Intel OTC