linux-kernel - Re: [PATCH v2 6/8] drm: Introduce drm_bridge_mode

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Date:   Wed, 10 May 2017 15:07:43 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
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>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Dave Airlie <airlied@...ux.ie>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Archit Taneja <architt@...eaurora.org>
Subject: Re: [PATCH v2 6/8] drm: Introduce drm_bridge_mode_valid()

Hi Ville,


On 10-05-2017 15:01, Jose Abreu wrote:
> Hi Ville,
>
>
> On 10-05-2017 14:41, Ville Syrjälä wrote:
>> On Tue, May 09, 2017 at 06:00:13PM +0100, Jose Abreu wrote:
>>> Introduce a new helper function which calls mode_valid() callback
>>> for all bridges in an encoder chain.
>>>
>>> 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>
>>> ---
>>>  drivers/gpu/drm/drm_bridge.c | 33 +++++++++++++++++++++++++++++++++
>>>  include/drm/drm_bridge.h     |  2 ++
>>>  2 files changed, 35 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
>>> index 86a7637..dc8cdfe 100644
>>> --- a/drivers/gpu/drm/drm_bridge.c
>>> +++ b/drivers/gpu/drm/drm_bridge.c
>>> @@ -206,6 +206,39 @@ bool drm_bridge_mode_fixup(struct drm_bridge *bridge,
>>>  EXPORT_SYMBOL(drm_bridge_mode_fixup);
>>>  
>>>  /**
>>> + * drm_bridge_mode_valid - validate the mode against all bridges in the
>>> + * 			   encoder chain.
>>> + * @bridge: bridge control structure
>>> + * @mode: desired mode to be validated
>>> + *
>>> + * Calls &drm_bridge_funcs.mode_valid for all the bridges in the encoder
>>> + * chain, starting from the first bridge to the last. If at least one bridge
>>> + * does not accept the mode the function returns the error code.
>>> + *
>>> + * Note: the bridge passed should be the one closest to the encoder.
>>> + *
>>> + * RETURNS:
>>> + * MODE_OK on success, drm_mode_status Enum error code on failure
>>> + */
>>> +enum drm_mode_status drm_bridge_mode_valid(struct drm_bridge *bridge,
>>> +					   const struct drm_display_mode *mode)
>>> +{
>>> +	enum drm_mode_status ret = MODE_OK;
>>> +
>>> +	if (!bridge)
>>> +		return ret;
>>> +
>>> +	if (bridge->funcs->mode_valid)
>>> +		ret = bridge->funcs->mode_valid(bridge, mode);
>>> +
>>> +	if (ret != MODE_OK)
>>> +		return ret;
>>> +
>>> +	return drm_bridge_mode_valid(bridge->next, mode);
>> Looks like it should be pretty trivial to avoid the recursion.
>>
>> Am I correct in interpreting this that bridges have some kind of
>> a hand rolled linked list implementation? Reusing the standard
>> linked lists would allow you to use list_for_each() etc.
> I reused the drm_bridge_mode_fixup but now I see how its done
> like that: so that the fixup is propagated in the correct order.
> As for mode_valid we just need to check if ret != MODE_OK then I
> think we can use the list_for_each_entry(bridge->list).

Oops, I got this wrong sorry. I meant there is a list but its for
all the system bridges. This is a "custom" linked list yeah.

Best regards,
Jose Miguel Abreu

>
> Best regards,
> Jose Miguel Abreu
>
>>> +}
>>> +EXPORT_SYMBOL(drm_bridge_mode_valid);
>>> +
>>> +/**
>>>   * drm_bridge_disable - disables all bridges in the encoder chain
>>>   * @bridge: bridge control structure
>>>   *
>>> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
>>> index 00c6c36..8358eb3 100644
>>> --- a/include/drm/drm_bridge.h
>>> +++ b/include/drm/drm_bridge.h
>>> @@ -233,6 +233,8 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>>>  bool drm_bridge_mode_fixup(struct drm_bridge *bridge,
>>>  			const struct drm_display_mode *mode,
>>>  			struct drm_display_mode *adjusted_mode);
>>> +enum drm_mode_status drm_bridge_mode_valid(struct drm_bridge *bridge,
>>> +					   const struct drm_display_mode *mode);
>>>  void drm_bridge_disable(struct drm_bridge *bridge);
>>>  void drm_bridge_post_disable(struct drm_bridge *bridge);
>>>  void drm_bridge_mode_set(struct drm_bridge *bridge,
>>> -- 
>>> 1.9.1
>>>