[alsa-devel] [PATCH 3/3] ALSA: hda - hdmi: Notify userspace when ELD control changes

[David Henningsson]

On 02/18/2013 03:55 PM, Takashi Iwai wrote:
> At Mon, 18 Feb 2013 15:46:04 +0100,
> David Henningsson wrote:
>>
>> On 02/18/2013 03:41 PM, Takashi Iwai wrote:
>>> At Mon, 18 Feb 2013 14:11:13 +0100,
>>> David Henningsson wrote:
>>>>
>>>> Since ELD sometimes becomes available a while after we have detected
>>>> presence, we need to be able to listen for changes on the ELD control.
>>>>
>>>> Signed-off-by: David Henningsson <david.henningsson at canonical.com>
>>>> ---
>>>>    sound/pci/hda/patch_hdmi.c |   10 ++++++++++
>>>>    1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
>>>> index 9236cdb..d3b1a93 100644
>>>> --- a/sound/pci/hda/patch_hdmi.c
>>>> +++ b/sound/pci/hda/patch_hdmi.c
>>>> @@ -74,6 +74,7 @@ struct hdmi_spec_per_pin {
>>>>
>>>>    	struct hda_codec *codec;
>>>>    	struct hdmi_eld sink_eld;
>>>> +	struct snd_kcontrol *eld_ctl;
>>>>    	struct delayed_work work;
>>>>    	int repoll_count;
>>>>    	bool non_pcm;
>>>> @@ -406,6 +407,7 @@ static int hdmi_create_eld_ctl(struct hda_codec *codec, int pin_idx,
>>>>    	if (err < 0)
>>>>    		return err;
>>>>
>>>> +	spec->pins[pin_idx].eld_ctl = kctl;
>>>>    	return 0;
>>>>    }
>>>>
>>>> @@ -1175,6 +1177,7 @@ static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll)
>>>>    	 */
>>>>    	int present = snd_hda_pin_sense(codec, pin_nid);
>>>>    	bool eld_valid = false;
>>>> +	bool old_eld_valid = eld->eld_valid;
>>>>
>>>>    	memset(eld, 0, offsetof(struct hdmi_eld, eld_buffer));
>>>>
>>>> @@ -1196,6 +1199,13 @@ static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll)
>>>>    					   msecs_to_jiffies(300));
>>>>    		}
>>>>    	}
>>>> +
>>>> +	if (eld->eld_valid != old_eld_valid && per_pin->eld_ctl) {
>>>> +		snd_ctl_notify(codec->bus->card,
>>>> +			       SNDRV_CTL_EVENT_MASK_VALUE | SNDRV_CTL_EVENT_MASK_INFO,
>>>> +			       &per_pin->eld_ctl->id);
>>>> +	}
>>>
>>> This notification should be skipped when the pin sensing is requeued.
>>
>> I don't understand this comment. Are you referring to repolling the ELD?
>
> Yes.
>
>> eld->eld_valid is never set to TRUE when repoll happens.
>
> But old_eld_valid might be TRUE, and you cleared eld->eld_valid to
> FALSE now before the actual probe result.  Thus the check above passes
> and sends a notification although the actual probe isn't done.

If old_eld_valid is true, then we're talking about an unplug event. Why 
would there be a repoll when the monitor has disappeared?

But yes, the patch is based on the fact that ELD info never actually 
changes from one valid state to another valid state, without being 
invalid in between. If you think that could actually happen, maybe I 
need to add a memory compare of the old and new ELDs?


-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic