On Mon, Jun 06, 2016 at 04:29:06PM +0300, Mika Kahola wrote:
> Helper routine to read out maximum supported pixel rate
> for DisplayPort legay VGA converter or TMDS clock rate
> for other digital legacy converters. The helper returns
> clock rate in kHz.
>
> Signed-off-by: Mika Kahola <mika.kahola@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_helper.c | 28 ++++++++++++++++++++++++++++
> include/drm/drm_dp_helper.h | 2 ++
> 2 files changed, 30 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 7d3b245..18b72eb 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -479,6 +479,34 @@ int drm_dp_downstream_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> }
> EXPORT_SYMBOL(drm_dp_downstream_type);
>
> +/**
> + * drm_dp_downstream_max_clock() - extract branch device max
> + * pixel rate for legacy VGA
> + * converter or max TMDS clock
> + * rate for others
> + * @dpcd: DisplayPort configuration data
> + * @port_cap: port capabilities
> + *
> + * Returns max clock in kHz on success or negative error code on failure
> + */
> +int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> + const u8 port_cap[4])
> +{
> + int type = drm_dp_downstream_type(dpcd, port_cap);
> + bool detailed_cap_info = dpcd[DP_DOWNSTREAMPORT_PRESENT] &
> + DP_DETAILED_CAP_INFO_AVAILABLE;
> +
> + if (detailed_cap_info) {
Could swap this over to an early return and then we don't have to indent
the actual meat of the function.
> + if (type == DP_DS_PORT_TYPE_VGA)
> + return port_cap[1] * 8 * 1000;
> + else if (type != DP_DS_PORT_TYPE_WIRELESS)
> + return port_cap[1] * 2500;
That's not correct. I suggest a switch() and deal with each type
explicitly.
> + }
> +
> + return -EINVAL;
I think I'd return 0 for the "we don't know" case. That way we can use
this directly without worrying about negative values.
> +}
> +EXPORT_SYMBOL(drm_dp_downstream_max_clock);
> +
> /*
> * I2C-over-AUX implementation
> */
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index f290829..c3324d3 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -810,6 +810,8 @@ int drm_dp_downstream_port_cap(struct drm_dp_aux *aux,
> const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> u8 port_cap[4]);
> int drm_dp_downstream_type(const u8 dpcd[DP_RECEIVER_CAP_SIZE], const u8 port_cap[4]);
> +int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
> + const u8 port_cap[4]);
>
> int drm_dp_aux_register(struct drm_dp_aux *aux);
> void drm_dp_aux_unregister(struct drm_dp_aux *aux);
> --
> 1.9.1
--
Ville Syrjälä
Intel OTC
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