ALSA: hda - hdmi: ELD shouldn't be valid after unplug

Currently, eld_valid is never set to false, except at kernel module
load time. This patch makes sure that eld is no longer valid when
the cable is (hot-)unplugged.

Cc: stable@kernel.org
Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - hdmi: Do not expose eld data when eld is invalid

Previously, it was possible to read the eld data of the previous
monitor connected. This should not be allowed.

Also refactor the function slightly.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - hdmi: Refactor hdmi_eld into parsed_hdmi_eld

For better readability, the information that is parsed out of the
ELD data is now put into a separate parsed_hdmi_eld struct.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - hdmi: Protect ELD buffer

Because the eld buffer can be simultaneously accessed from both
workqueue context (updating) and process context (kcontrol read),
we need to protect it with a mutex to guarantee consistency.

To avoid holding the mutex while reading the ELD info from the
codec, we introduce a temporary eld buffer.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
ALSA: hda - hdmi: Notify userspace when ELD control changes

ELD validity can change during the lifetime of a presence detect,
so we need to be able to listen for changes on the ELD control.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>