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

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Date:   Wed, 10 May 2017 15:01:35 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        "Jose Abreu" <Jose.Abreu@...opsys.com>
CC:     <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 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).

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
>>