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From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date: Thu, 7 Mar 2024 22:40:56 +0200
Message-ID: <CAA8EJppTcPO3j7GpGcGbKPUjQ=3rTMMOrU1SYR3mtkWLztf2qQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/4] drm/bridge: Add fwnode based helpers to get the
 next bridge
To: Sui Jingfeng <sui.jingfeng@linux.dev>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>, Neil Armstrong <neil.armstrong@linaro.org>, 
	Robert Foss <rfoss@kernel.org>, Laurent Pinchart <Laurent.pinchart@ideasonboard.com>, 
	Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@gmail.com>, 
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, 
	Thomas Zimmermann <tzimmermann@suse.de>, David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
	Phong LE <ple@baylibre.com>, dri-devel@lists.freedesktop.org, 
	linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

On Thu, 7 Mar 2024 at 22:32, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
>
> Hi,
>
>
> On 2024/3/8 03:37, Dmitry Baryshkov wrote:
> > On Thu, 7 Mar 2024 at 21:20, Sui Jingfeng <sui.jingfeng@linux.dev> wrote:
> >> Hi,
> >>
> >>
> >> On 2024/3/8 02:43, Dmitry Baryshkov wrote:
> >>>> +
> >>>>    MODULE_AUTHOR("Ajay Kumar<ajaykumar.rs@samsung.com>");
> >>>>    MODULE_DESCRIPTION("DRM bridge infrastructure");
> >>>>    MODULE_LICENSE("GPL and additional rights");
> >>>> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> >>>> index 3606e1a7f965..d4c95afdd662 100644
> >>>> --- a/include/drm/drm_bridge.h
> >>>> +++ b/include/drm/drm_bridge.h
> >>>> @@ -26,6 +26,7 @@
> >>>>    #include <linux/ctype.h>
> >>>>    #include <linux/list.h>
> >>>>    #include <linux/mutex.h>
> >>>> +#include <linux/of.h>
> >>>>
> >>>>    #include <drm/drm_atomic.h>
> >>>>    #include <drm/drm_encoder.h>
> >>>> @@ -721,6 +722,8 @@ struct drm_bridge {
> >>>>           struct list_head chain_node;
> >>>>           /** @of_node: device node pointer to the bridge */
> >>>>           struct device_node *of_node;
> >>> In my opinion, if you are adding fwnode, we can drop of_node
> >>> completely. There is no need to keep both of them.
> >>
> >> But the 'struct device' have both of them contained, we should *follow the core*, right?
> >> They are two major firmware subsystems (DT and ACPT), both are great and large, right?
> >> Personally, I think the drm_bridge should embeds 'struct device', after all, drm bridge
> >> are mainly stand for display bridges device. And also to reflect what you said: "to
> >> reflect the hardware perfectly" and remove some boilerplate.
> > struct device contains both because it is at the root of the hierarchy
> > and it should support both API. drm_bridge is a consumer, so it's fine
> > to have just one.
> >
>
> What I really means is that
> if one day a 'struct device *dev' is embedded into struct drm_bridge,
> we only need to improve(modify) the implement ofdrm_bridge_set_node().
> This is *key point*. Currently, they(of_node and fwnode) point to the
> same thing, it is also fine.
>
> For the various drm bridge drivers implementations, the 'struct drm_bridge'
> is also belong to the driver core category. drm bridges are also play the
> producer role.
>
> >> I think I'm not good enough to do such a big refactor, sorry. I believe that Maxime
> >> and Laurent are the advanced programmers who is good enough to do such things, maybe
> >> you can ask them for help?
> > Well, you picked up the task ;-)
>
>
> Well, my subject(title) is "*Allow* to use fwnode based API to get drm bridges".
> not "Replace 'OF' with fwnode", My task is to provide an alternative solution
> for the possible users. And to help improve code sharing and improve code reuse.
> And remove some boilerplate. Others things beyond that is not being taken by
> anybody. Thanks.

Ok, I'd defer this to the maintainers decision then.

>
>
> >
> > But really, there is nothing so hard about it:
> > - Change of_node to fw_node, apply an automatic patch changing this in
> > bridge drivers.
> > - Make drm_of_bridge functions convert passed of_node and comp
> >
> > After this we can start cleaning up bridge drivers to use fw_node API
> > natively as you did in your patches 2-4.
>
>
> Yes, it's not so hard. But I'm a little busy due to other downstream developing
> tasks. Sorry, very sorry!
>
> During the talk with you, I observed that you are very good at fwnode domain.
> Are you willing to help the community to do something? For example, currently
> the modern drm bridge framework is corrupted by legacy implement, is it possible
> for us to migrate them to modern? Instead of rotting there? such as the lontium-lt9611uxc.c
> which create a drm connector manually, not modernized yet and it's DT dependent.
> So, there are a lot things to do.

Actually, lontium-lt9611uxc.c does both of that ;-) It supports
creating a connector and it as well supports attaching to a chain
without creating a connector. Pretty nice, isn't it?


-- 
With best wishes
Dmitry