linux-kernel - Re: [PATCH v2 1/8] drm: Add crtc/encoder/bridge->mode

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Message-ID: <ca4812b9-4b93-6c59-f170-03b4e37ec828@synopsys.com>
Date:   Wed, 10 May 2017 10:05:08 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
CC:     Jose Abreu <Jose.Abreu@...opsys.com>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Dave Airlie <airlied@...ux.ie>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Archit Taneja <architt@...eaurora.org>
Subject: Re: [PATCH v2 1/8] drm: Add crtc/encoder/bridge->mode_valid()
 callbacks

Hi Daniel,


On 10-05-2017 09:03, Daniel Vetter wrote:
> On Tue, May 09, 2017 at 06:00:08PM +0100, Jose Abreu wrote:
>> This adds a new callback to crtc, encoder and bridge helper functions
>> called mode_valid(). This callback shall be implemented if the
>> corresponding component has some sort of restriction in the modes
>> that can be displayed. A NULL callback implicates that the component
>> can display all the modes.
>>
>> We also change the description of connector->mode_valid() callback
>> so that it matches the existing behaviour: It is never called in
>> atomic check phase.
>>
>> Only the callbacks were implemented to simplify review process,
>> following patches will make use of them.
>>
>> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
>> Cc: Carlos Palminha <palminha@...opsys.com>
>> Cc: Alexey Brodkin <abrodkin@...opsys.com>
>> Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
>> Cc: Dave Airlie <airlied@...ux.ie>
>> Cc: Andrzej Hajda <a.hajda@...sung.com>
>> Cc: Archit Taneja <architt@...eaurora.org>
>> ---
>>
>> Changes v1->v2:
>> 	- Change description of connector->mode_valid() (Daniel)
>>
>>  include/drm/drm_bridge.h                 | 20 ++++++++++++++
>>  include/drm/drm_modeset_helper_vtables.h | 45 ++++++++++++++++++++++++++++++++
>>  2 files changed, 65 insertions(+)
>>
>> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
>> index fdd82fc..00c6c36 100644
>> --- a/include/drm/drm_bridge.h
>> +++ b/include/drm/drm_bridge.h
>> @@ -59,6 +59,26 @@ struct drm_bridge_funcs {
>>  	void (*detach)(struct drm_bridge *bridge);
>>  
>>  	/**
>> +	 * @mode_valid:
>> +	 *
>> +	 * This callback is used to check if a specific mode is valid in this
>> +	 * bridge. This should be implemented if the bridge has some sort of
>> +	 * restriction in the modes it can display. For example, a given bridge
>> +	 * may be responsible to set a clock value. If the clock can not
>> +	 * produce all the values for the available modes then this callback
>> +	 * can be used to restrict the number of modes to only the ones that
>> +	 * can be displayed.
>> +	 *
>> +	 * This is called at mode probe and at atomic check phase.
>> +	 *
>> +	 * RETURNS:
>> +	 *
>> +	 * drm_mode_status Enum
>> +	 */
>> +	enum drm_mode_status (*mode_valid)(struct drm_bridge *crtc,
>> +					   const struct drm_display_mode *mode);
>> +
>> +	/**
>>  	 * @mode_fixup:
>>  	 *
>>  	 * This callback is used to validate and adjust a mode. The paramater
>> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
>> index c01c328..eec2c70 100644
>> --- a/include/drm/drm_modeset_helper_vtables.h
>> +++ b/include/drm/drm_modeset_helper_vtables.h
>> @@ -106,6 +106,26 @@ struct drm_crtc_helper_funcs {
>>  	void (*commit)(struct drm_crtc *crtc);
>>  
>>  	/**
>> +	 * @mode_valid:
>> +	 *
>> +	 * This callback is used to check if a specific mode is valid in this
>> +	 * crtc. This should be implemented if the crtc has some sort of
>> +	 * restriction in the modes it can display. For example, a given crtc
>> +	 * may be responsible to set a clock value. If the clock can not
>> +	 * produce all the values for the available modes then this callback
>> +	 * can be used to restrict the number of modes to only the ones that
>> +	 * can be displayed.
>> +	 *
>> +	 * This is called at mode probe and at atomic check phase.
>> +	 *
>> +	 * RETURNS:
>> +	 *
>> +	 * drm_mode_status Enum
>> +	 */
>> +	enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc,
>> +					   const struct drm_display_mode *mode);
>> +
>> +	/**
>>  	 * @mode_fixup:
>>  	 *
>>  	 * This callback is used to validate a mode. The parameter mode is the
>> @@ -457,6 +477,26 @@ struct drm_encoder_helper_funcs {
>>  	void (*dpms)(struct drm_encoder *encoder, int mode);
>>  
>>  	/**
>> +	 * @mode_valid:
>> +	 *
>> +	 * This callback is used to check if a specific mode is valid in this
>> +	 * encoder. This should be implemented if the encoder has some sort
>> +	 * of restriction in the modes it can display. For example, a given
>> +	 * encoder may be responsible to set a clock value. If the clock can
>> +	 * not produce all the values for the available modes then this callback
>> +	 * can be used to restrict the number of modes to only the ones that
>> +	 * can be displayed.
>> +	 *
>> +	 * This is called at mode probe and at atomic check phase.
>> +	 *
>> +	 * RETURNS:
>> +	 *
>> +	 * drm_mode_status Enum
>> +	 */
>> +	enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
>> +					   const struct drm_display_mode *mode);
>> +
>> +	/**
>>  	 * @mode_fixup:
>>  	 *
>>  	 * This callback is used to validate and adjust a mode. The parameter
>> @@ -795,6 +835,11 @@ struct drm_connector_helper_funcs {
>>  	 * (which is usually derived from the EDID data block from the sink).
>>  	 * See e.g. drm_helper_probe_single_connector_modes().
>>  	 *
>> +	 * This callback is never called in atomic check phase so that userspace
>> +	 * can override kernel sink checks in case of broken EDID with wrong
>> +	 * limits from the sink. You can use the remaining mode_valid()
>> +	 * callbacks to validate the mode against your video path.
>> +	 *
>>  	 * NOTE:
>>  	 *
>>  	 * This only filters the mode list supplied to userspace in the
> Kerneldoc review seems to still be missing. One case that needs to be
> updated is this note here. But there's a pile of other places where we
> reference one of the mode_valid or mode_fixup functions, and they should
> all be updated.
>
> Also, it'd be good to explain what to put into mode_valid and what to put
> into mode_fixup, for objects which have both. I can help with this, but I
> think it'd be good if you make a first round, since that might catch some
> interactions we've missed.
>
> Thanks, Daniel

Ok, I will need some time to review and update this. I think
until the end of this week I will have another version to send.
Thanks!

Best regards,
Jose Miguel Abreu