linux-kernel - Re: [RFC PATCH v1 0/4] Add Rockchip RGA support

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Message-ID: <56FA69C5.5090602@rock-chips.com>
Date:	Tue, 29 Mar 2016 19:40:53 +0800
From:	Yakir Yang <ykk@...k-chips.com>
To:	Emil Velikov <emil.l.velikov@...il.com>,
	Heiko Stuebner <heiko@...ech.de>
Cc:	David Airlie <airlied@...ux.ie>,
	Mark Yao <mark.yao@...k-chips.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Russell King <linux@....linux.org.uk>,
	devicetree <devicetree@...r.kernel.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	ML dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v1 0/4] Add Rockchip RGA support

Hi Emil,

On 03/28/2016 08:21 PM, Emil Velikov wrote:
> On 22 March 2016 at 00:42, Heiko Stuebner <heiko@...ech.de> wrote:
>> Hi Yakir,
>>
>> Am Montag, 21. März 2016, 20:17:46 schrieb Yakir Yang:
>>> On 03/21/2016 07:29 PM, Heiko Stübner wrote:
>>>> Am Montag, 21. März 2016, 17:28:38 schrieb Yakir Yang:
>>>>> This patch set would add the RGA direct rendering based 2d graphics
>>>>> acceleration module.
>>>> very cool to see that.
>>> ;)
>>>
>>>>> This patch set is based on git repository below:
>>>>> git://people.freedesktop.org/~airlied/linux drm-next
>>>>> commit id: 568d7c764ae01f3706085ac8f0d8a8ac7e826bd7
>>>>>
>>>>> And the RGA driver is based on Exynos G2D driver, it only manages the
>>>>> command lists received from user, so user should make the command list
>>>>> to data and registers needed by operation to use.
>>>>>
>>>>> I have prepared an userspace demo application for testing:
>>>>>     https://github.com/yakir-Yang/libdrm-rockchip
>>>>>
>>>>> That is a rockchip libdrm library, and I have write a simple test case
>>>>> "rockchip_rga_test" that would test the below RGA features:
>>>>> - solid
>>>>> - copy
>>>>> - rotation
>>>>> - flip
>>>>> - window clip
>>>>> - dithering
>>>> Did you submit your libdrm changes as well?
>>>>
>>>> Userspace-interfaces need to be stable so the other side must also get
>>>> accepted - even before the kernel change if I remember correctly.
>>> Got it, and I just saw exynos_fimg2d already landed at mainline libdrm.
>>> But I don't find the way to submit patches to libdrm, would you like
>>> share some helps here ;)
>> Looking at the libdrm sources on cgit.freedesktop.org, I did not find any
>> specific manual on submitting patches.
>>
>> But looking at the dri-list archive, dri-devel@...ts.freedesktop.org is the
>> right list and looking at the libdrm history it looks like Emil Velikov
>> <emil.l.velikov@...il.com> seems to be doing maintenance-stuff in libdrm.
>> And as a 3rd recipient, please also include the linux-rockchip list.
>>
>> @Emil, please shout if I read that wrong :-)
>>
> You got it spot on Heiko. There are a few notes though...
>
> As one reuses the existing hardware/IP block, it would be better to
> avoid copy/pasting code around.
> Namely:
>   - (if possible) factor out the exynos g2d kernel functionality to a
> separate kernel module and wire up the rockhip (via dt ?) to use it
>   - factor out the g2d specifics out of exynos_drm.h (into
> exynos_g2d_drm.h perhaps ?) and make sure exynos_drm.h includes the
> new header
>   - if neither of these are possible, then please ensure that the new
> header uses correct types (see the docs [1]), use MIT/X11 license (if
> possible) and link where upstream userspace is happy with the
> interface (ideally more than a simple test app like libdrm)

Whops... you have provided the third choice, nice  :-D

And I got little idea about license, where should I use the MIT/X11
license, should I declare the MIT/X11 license in kernel uapi head
file, but Andreas just remind that kernel do not allow to no GUN
license. Or may be I can:
1. Use GUN license in kernel rockchip_drm.h uapi head file
2. Use MIT/X11 license in libdrm rockchip_drm.h head file.

And I don't understand the "link where upstream userspace is happy
with the interface", could you reference small example here.

Thanks,
- Yakir

> These might sound like an overkill, although getting UAPI right and
> maintaining it forever forces us to do so.
>
> Regards,
> Emil
>
> [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/ioctl/botching-up-ioctls.txt
>
>
>