[Lets see if I have a working vpn connection today...]
On Sun, 19 Sep 2010 14:52:06 +0800, Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx> wrote:
> To help to determine if digital display port needs to enable
> audio output or not. This one adds a helper to get monitor's
> audio capability via EDID CEA extension block.
>
> Tested-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Signed-off-by: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
This should be cc'ed for Adam Jackson's attention as well.
> ---
> drivers/gpu/drm/drm_edid.c | 92 +++++++++++++++++++++++++++++++++++++-------
> include/drm/drm_crtc.h | 1 +
> 2 files changed, 79 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 96e9631..7f356af 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -1268,34 +1268,51 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
> }
>
> #define HDMI_IDENTIFIER 0x000C03
> +#define AUDIO_BLOCK 0x01
> #define VENDOR_BLOCK 0x03
> +#define EDID_BASIC_AUDIO (1 << 6)
> +
> /**
> + * drm_detect_monitor_audio - check monitor audio capability
> + *
> + * Monitor should have CEA extension block.
> + * If monitor has 'basic audio', but no CEA audio blocks, it's 'basic
> + * audio' only. If there is any audio extension block and supported
> + * audio format, assume at least 'basic audio' support, even if 'basic
> + * audio' is not defined in EDID.
> + *
> + */
> +bool drm_detect_monitor_audio(struct edid *edid)
drm_edid_has_monitor_audio()? That is a little more self-descriptive.
(I also think drm_detect_hdmi_monitor is poorly named.)
> +{
> + u8 *edid_ext;
> + int i, j;
> + bool has_audio = false;
> + int start_offset, end_offset;
> +
> + edid_ext = drm_find_cea_extension(edid);
> + if (!edid_ext)
> + goto end;
> +
> + has_audio = ((edid_ext[3] & EDID_BASIC_AUDIO) != 0);
Too many brackets do not lead to code clarity. ;-)
> +
> + if (has_audio) {
The last time Adam had a chance to comment on this EDID check, he
suggested that we cannot rely on has_audio being a reliable indicator of
the sink's properties. If the EDID has no audio support, then return
early, otherwise perform the secondary check that extension block contains
audio data.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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