Re: [PATCH 07/14] drm/amd/display: Implement DDC probe over AUX channel

[Alex Hung <alex.hung@amd.com>]

On 1/26/26 14:08, Timur Kristóf wrote:
> DDC probe means that we use the DDC (Display Data Channel) to
> verify whether a display is connected or not.
> 
> This was written with mainly analog connectors in mind, so it
> didn't work over the AUX channel. However, in order to support
> external DP bridge encoders found in CIK APUs, it needs to work
> over the AUX channel too.
> 
> Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
> ---
>   drivers/gpu/drm/amd/display/dc/link/link_detection.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/link/link_detection.c b/drivers/gpu/drm/amd/display/dc/link/link_detection.c
> index 1585cce65b0e..e1d568905581 100644
> --- a/drivers/gpu/drm/amd/display/dc/link/link_detection.c
> +++ b/drivers/gpu/drm/amd/display/dc/link/link_detection.c
> @@ -903,11 +903,18 @@ static bool link_detect_evaluate_edid_header(uint8_t edid_header[8])
>    */
>   static bool link_detect_ddc_probe(struct dc_link *link)
>   {
> +	enum signal_type signal = link_detect_sink_signal_type(link, DETECT_REASON_HPD);
> +	enum ddc_transaction_type transaction_type = get_ddc_transaction_type(signal);
> +
>   	if (!link->ddc)
>   		return false;
>   
> +	set_ddc_transaction_type(link->ddc, transaction_type);
> +
>   	uint8_t edid_header[8] = {0};
> -	bool ddc_probed = i2c_read(link->ddc, 0x50, edid_header, sizeof(edid_header));
> +	uint8_t zero = 0;
> +	bool ddc_probed =
> +		link_query_ddc_data(link->ddc, 0x50, &zero, 1, edid_header, sizeof(edid_header));

Please move variable declaration to beginning of the function. Thanks.

>   
>   	if (!ddc_probed)
>   		return false;