[(repost),2/5] drm_dp_cec: add note about good MegaChips 2900 CEC support

Submitted by Hans Verkuil on Aug. 17, 2018, 2:11 p.m.

Details

Message ID 20180817141122.9541-3-hverkuil@xs4all.nl
State New
Headers show
Series "drm/nouveau+amdgpu: add DP CEC-Tunneling-over-AUX (repost)" ( rev: 1 ) in Nouveau

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Commit Message

Hans Verkuil Aug. 17, 2018, 2:11 p.m.
From: Hans Verkuil <hans.verkuil@cisco.com>

A big problem with DP CEC-Tunneling-over-AUX is that it is tricky
to find adapters with a chipset that supports this AND where the
manufacturer actually connected the HDMI CEC line to the chipset.

Add a mention of the MegaChips 2900 chipset which seems to support
this feature well.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
---
 drivers/gpu/drm/drm_dp_cec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
index 1407b13a8d5d..8a718f85079a 100644
--- a/drivers/gpu/drm/drm_dp_cec.c
+++ b/drivers/gpu/drm/drm_dp_cec.c
@@ -16,7 +16,9 @@ 
  * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
  * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
  * Parade PS176), but they do not wire up the CEC pin, thus making CEC
- * useless.
+ * useless. Note that MegaChips 2900-based adapters appear to have good
+ * support for CEC tunneling. Those adapters that I have tested using
+ * this chipset all have the CEC line connected.
  *
  * Sadly there is no way for this driver to know this. What happens is
  * that a /dev/cecX device is created that is isolated and unable to see

Comments

Reviewed-by: Lyude Paul <lyude@redhat.com>

On Fri, 2018-08-17 at 16:11 +0200, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> A big problem with DP CEC-Tunneling-over-AUX is that it is tricky
> to find adapters with a chipset that supports this AND where the
> manufacturer actually connected the HDMI CEC line to the chipset.
> 
> Add a mention of the MegaChips 2900 chipset which seems to support
> this feature well.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> ---
>  drivers/gpu/drm/drm_dp_cec.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
> index 1407b13a8d5d..8a718f85079a 100644
> --- a/drivers/gpu/drm/drm_dp_cec.c
> +++ b/drivers/gpu/drm/drm_dp_cec.c
> @@ -16,7 +16,9 @@
>   * here. Quite a few active (mini-)DP-to-HDMI or USB-C-to-HDMI adapters
>   * have a converter chip that supports CEC-Tunneling-over-AUX (usually the
>   * Parade PS176), but they do not wire up the CEC pin, thus making CEC
> - * useless.
> + * useless. Note that MegaChips 2900-based adapters appear to have good
> + * support for CEC tunneling. Those adapters that I have tested using
> + * this chipset all have the CEC line connected.
>   *
>   * Sadly there is no way for this driver to know this. What happens is
>   * that a /dev/cecX device is created that is isolated and unable to see