Re: [PATCH V7 03/12] drm/bridge: Add helper functions for drm_bridge

From: Andrzej Hajda <a.hajda@samsung.com>
To: Daniel Vetter <daniel@ffwll.ch>,
	Thierry Reding <thierry.reding@gmail.com>
Cc: linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	Jingoo Han <jg1.han@samsung.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Ajay kumar <ajaynumb@gmail.com>,
	Pannaga Bhushan Reddy Patel <bhushan.r@samsung.com>,
	Prashanth G <prashanth.g@samsung.com>,
	Ajay Kumar <ajaykumar.rs@samsung.com>
Subject: Re: [PATCH V7 03/12] drm/bridge: Add helper functions for drm_bridge
Date: Wed, 29 Oct 2014 10:09:04 +0100	[thread overview]
Message-ID: <5450AEB0.9070507@samsung.com> (raw)
In-Reply-To: <20141029075823.GN26941@phenom.ffwll.local>

On 10/29/2014 08:58 AM, Daniel Vetter wrote:
> On Tue, Oct 28, 2014 at 04:05:34PM +0100, Thierry Reding wrote:
>> On Tue, Oct 28, 2014 at 08:16:44PM +0530, Ajay kumar wrote:
>>> On Tue, Oct 28, 2014 at 8:11 PM, Thierry Reding
>>> <thierry.reding@gmail.com> wrote:
>>>> On Tue, Oct 28, 2014 at 03:19:36PM +0100, Daniel Vetter wrote:
>>>>> On Tue, Oct 28, 2014 at 1:28 PM, Ajay kumar <ajaynumb@gmail.com> wrote:
>>>>>> On Tue, Oct 28, 2014 at 3:31 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>> [...]
>>>>>>> Hm, if you do this can you pls also update drm_panel accordingly? It
>>>>>>> shouldn't be a lot of fuzz and would make things around drm+dt more
>>>>>>> consistent.
>>>>>> Are you talking about using struct device_node instead of struct device?
>>>>>> I guess you have misplaced the comment under the wrong section!
>>>>>
>>>>> Yeah, that should have been one up ;-)
>>>>
>>>> Like I said earlier, I don't think dropping struct device * in favour of
>>>> struct device_node * is a good idea.
>>> I am not sure about drm_panel.
>>> But, I am not really doing anything with the struct device pointer in
>>> case of bridge.
>>> So, just wondering if it is really needed?
>>
>> I think it's useful to have it just to send the right message. DRM panel
>> and DRM bridge aren't specific to device tree. They are completely
>> generic and can work with any type of device, whether it was
>> instantiated from the device tree or some other infrastructure. Dropping
>> struct device * will make it effectively useless on anything but DT. I
>> don't think we should strive for that, even if only DT-enabled platforms
>> currently use them.
> 
> See my other reply, but I now think we should put neither into drm
> structures. This "find me the driver structures for this device" problem
> looks really generic, and it has nothing to do with the drm structures and
> concepts like bridges/panels at all. It shouldn't be in there at all.
> 
> Adding it looks very much like reintroducing the drm midlayer that we just
> finally made obsolete, just not at the top-level (struct drm_device) but
> at a bunch of leaf nodes. I expect all the same issues though. And I'm
> definitely not looking to de-midlayer more stuff that we're just adding.
> 
> Imo this should be solved as a separate helper thing, maybe in the driver
> core akin to the component helpers from Russell.
> -Daniel
> 

As I understand you want something generic to look for panels, bridges,
whatever and, like components, it should allow to safe hot plug/unplug.
I have proposed such thing few months ago [1]. Have you looked at it?

[1]: https://lkml.org/lkml/2014/4/30/345

Regards
Andrzej
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