On 11/29/2016 11:27 PM, Laurent Pinchart wrote:
> Hi Archit,
>
> On Tuesday 29 Nov 2016 15:57:06 Archit Taneja wrote:
>> On 11/29/2016 02:34 PM, Laurent Pinchart wrote:
>>> Instead of linking encoders and bridges in every driver (and getting it
>>> wrong half of the time, as many drivers forget to set the drm_bridge
>>> encoder pointer), do so in core code. The drm_bridge_attach() function
>>> needs the encoder and optional previous bridge to perform that task,
>>> update all the callers.
>>>
>>> Signed-off-by: Laurent Pinchart
>>> <laurent.pinchart+renesas at ideasonboard.com>
>>> ---
>>>
>>> drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 4 +-
>>> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 4 +-
>>> drivers/gpu/drm/bridge/dw-hdmi.c | 3 +-
>>> drivers/gpu/drm/drm_bridge.c | 46 ++++++++++++-----
>>> drivers/gpu/drm/drm_simple_kms_helper.c | 4 +-
>>> drivers/gpu/drm/exynos/exynos_dp.c | 5 +--
>>> drivers/gpu/drm/exynos/exynos_drm_dsi.c | 6 +--
>>> drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c | 5 +--
>>> drivers/gpu/drm/hisilicon/kirin/dw_drm_dsi.c | 5 +--
>>> drivers/gpu/drm/imx/imx-ldb.c | 6 +--
>>> drivers/gpu/drm/imx/parallel-display.c | 4 +-
>>> drivers/gpu/drm/mediatek/mtk_dpi.c | 8 ++--
>>> drivers/gpu/drm/mediatek/mtk_dsi.c | 24 ++---------
>>> drivers/gpu/drm/mediatek/mtk_hdmi.c | 11 +++---
>>> drivers/gpu/drm/msm/dsi/dsi_manager.c | 17 +++++---
>>> drivers/gpu/drm/msm/edp/edp_bridge.c | 2 +-
>>> drivers/gpu/drm/msm/hdmi/hdmi_bridge.c | 2 +-
>>> drivers/gpu/drm/rcar-du/rcar_du_hdmienc.c | 5 +--
>>> drivers/gpu/drm/sti/sti_dvo.c | 3 +-
>>> drivers/gpu/drm/sti/sti_hda.c | 3 +-
>>> drivers/gpu/drm/sti/sti_hdmi.c | 3 +-
>>> drivers/gpu/drm/sun4i/sun4i_rgb.c | 13 +++---
>>> include/drm/drm_bridge.h | 3 +-
>>> 23 files changed, 83 insertions(+), 103 deletions(-)
>
> [snip]
>
>>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
>>> index 0ee052b7c21a..850bd6509ef1 100644
>>> --- a/drivers/gpu/drm/drm_bridge.c
>>> +++ b/drivers/gpu/drm/drm_bridge.c
>
> [snip]
>
>>> @@ -92,32 +93,53 @@ void drm_bridge_remove(struct drm_bridge *bridge)
>>> EXPORT_SYMBOL(drm_bridge_remove);
>>>
>>> /**
>>> - * drm_bridge_attach - associate given bridge to our DRM device
>>> + * drm_bridge_attach - attach the bridge to an encoder's chain
>>> *
>>> - * @dev: DRM device
>>> - * @bridge: bridge control structure
>>> + * @encoder: DRM encoder
>>> + * @bridge: bridge to attach
>>> + * @previous: previous bridge in the chain (optional)
>>> *
>>> - * Called by a kms driver to link one of our encoder/bridge to the given
>>> - * bridge.
>>> + * Called by a kms driver to link the bridge to an encoder's chain. The
>>> previous
>>> + * argument specifies the previous bridge in the chain. If NULL, the
>>> bridge is
>>> + * linked directly at the encoder's output. Otherwise it is linked at the
>>> + * previous bridge's output.
>>> *
>>> - * Note that setting up links between the bridge and our encoder/bridge
>>> - * objects needs to be handled by the kms driver itself.
>>> + * If non-NULL the previous bridge must be already attached by a call to
>>> this
>>> + * function.
>>> *
>>> * RETURNS:
>>> * Zero on success, error code on failure
>>> */
>>> -int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
>>> +int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge
>>> *bridge,
>>> + struct drm_bridge *previous)
>>> {
>>> - if (!dev || !bridge)
>>> + int ret;
>>> +
>>> + if (!encoder || !bridge)
>>> + return -EINVAL;
>>
>> I think we could derive previous from the encoder itself. Something like:
>>
>> previous = encoder->bridge;
>> while (previous && previous->next)
>> previous = previous->next;
>
> That's a very good point. It would however prevent us from catching drivers
> that attach bridges in the wrong order, which the !previous->dev currently
> allows us to do (and it should be turned into a WARN_ON as Daniel proposed).
>
With the simpler API, I don't think we will ever hit the case of
!previous->dev. The previous bridge (if it exists) in the chain would
already have a dev attached to it. In other words, we would remove the
risk of the chance of the 'previous' bridge being unattached.
I'm a bit unclear about what you mean about the order part. If a kms driver
wants to create a chain: encoder->bridge1->bridge2, it should ideally do:
drm_bridge_attach(encoder, bridge1, NULL);
drm_bridge_attach(encoder, bridge2, bridge1);
We can't do much if the kms driver does the opposite:
drm_bridge_attach(encoder, bridge2, NULL);
drm_bridge_attach(encoder, bridge2, bridge1);
> I'm fine losing that ability, as your proposal makes the API simpler. I'll let
> you decide, which option do you prefer ?
I prefer the simpler API. I guess the main aim of the patch was to prevent the
driver setting up the encoder<->bridge links, which will be done anyway.
Thanks,
Archit
>
>>> +
>>> + if (previous && (!previous->dev || previous->encoder != encoder))
>>> return -EINVAL;
>>>
>>> if (bridge->dev)
>>> return -EBUSY;
>>>
>>> - bridge->dev = dev;
>>> + bridge->dev = encoder->dev;
>>> + bridge->encoder = encoder;
>>> +
>>> + if (bridge->funcs->attach) {
>>> + ret = bridge->funcs->attach(bridge);
>>> + if (ret < 0) {
>>> + bridge->dev = NULL;
>>> + bridge->encoder = NULL;
>>> + return ret;
>>> + }
>>> + }
>>>
>>> - if (bridge->funcs->attach)
>>> - return bridge->funcs->attach(bridge);
>>> + if (previous)
>>> + previous->next = bridge;
>>> + else
>>> + encoder->bridge = bridge;
>>>
>>> return 0;
>>> }
>>
>> <snip>
>
--
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