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

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Message-ID: <CACvgo513q-Vtm2wG4Cwh4G1u0OUNVAAFmHFv-kg4fHDEy7i_eg@mail.gmail.com>
Date:	Mon, 28 Mar 2016 13:21:02 +0100
From:	Emil Velikov <emil.l.velikov@...il.com>
To:	Heiko Stuebner <heiko@...ech.de>
Cc:	Yakir Yang <ykk@...k-chips.com>, 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

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)

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