Re: [alsa-devel] [PATCH v6 03/15] ASoC: hdac_hdmi: Enable DP1.2 and all converters/pins

On Mon, 15 Feb 2016 21:10:49 +0100, Mark Brown wrote:

On Fri, Feb 12, 2016 at 07:46:03AM +0530, Subhransu S. Prusty wrote:

...

+static void hdac_hdmi_skl_enable_all_pins(struct hdac_device *hdac) +{

• unsigned int vendor_param;
• vendor_param = snd_hdac_codec_read(hdac, INTEL_VENDOR_NID, 0,

• 		INTEL_GET_VENDOR_VERB, 0);
  

• if (vendor_param == -1 || vendor_param & INTEL_EN_ALL_PIN_CVTS)

• return;
  

• vendor_param |= INTEL_EN_ALL_PIN_CVTS;
• vendor_param = snd_hdac_codec_read(hdac, INTEL_VENDOR_NID, 0,

• 		INTEL_SET_VENDOR_VERB, vendor_param);
  

• if (vendor_param == -1)

• return;
  

+}

So to enable the pins we do a read? That seems... innovative. :/

It's a weird nature of HD-audio verb handling. While *_write() just sends the verb asynchronously, *_read() sends the verb, does sync and read-back the return value. But both read and write may handle the same verb.

Takashi