linux-kernel - Re: [PATCH 3/3 v2] drm/i915: hot plug/unplug notification to HDMI audio driver

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Date:	Mon, 21 Nov 2011 08:55:43 -0800
From:	Keith Packard <keithp@...thp.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Takashi Iwai <tiwai@...e.de>,
	"Wang\, Zhenyu Z" <zhenyu.z.wang@...el.com>,
	"dri-devel\@lists.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"intel-gfx\@lists.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3 v2] drm/i915: hot plug/unplug notification to HDMI audio driver

On Mon, 21 Nov 2011 14:37:49 +0800, Wu Fengguang <fengguang.wu@...el.com> wrote:
> On monitor hot plug/unplug, update ELD and set/clear SDVO_AUDIO_ENABLE
> or DP_AUDIO_OUTPUT_ENABLE accordingly.  So that the audio driver will
> receive hot plug events and take action to refresh its device state and
> ELD contents.
> 
> A new callback ->hotplug() is added to struct drm_connector_funcs which
> will be called immediately after ->detect() knowing that the monitor is
> either plugged or unplugged.
> 
> It's noticed that X may not call ->mode_set() at monitor hot plug, so it's
> necessary to call drm_edid_to_eld() earlier at ->detect() time rather than
> in intel_ddc_get_modes(), so that intel_write_eld() can see the new ELD
> in ->hotplug.

The X environment will eventually call mode_set when the user
environment decides to use the monitor. Any audio bits can, and should,
await the user's choice of a video mode before choosing the audio format
to use. We should not be adding eld information until the monitor is in
use.

-- 
keith.packard@...el.com

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