Require for drm control-node

[Christian König]

Hi Jared,

> I met a problem that the kmssink will have permission issue when 
> running with x11 and wayland.
This is intentional, at least with the current DRM KMS API design only 
one application is allowed to control a DRM device.

> So I’m change the code to use control node “controlD64” for display 
> and file node card0 for memory management. It work really well.
That sounds like a rather big bug to me, as far as I know control nodes 
are completely deprecated and should never be used concurrently with the 
DRM master on the primary node.

What hardware are trying this on?

Regards,
Christian.

Am 10.08.2017 um 10:27 schrieb Jared Hu:
>
> Hi All,
>
> I’m a gstreamer developer and is trying to implement a video display 
> plugin based on DRM/KMS which is named “kmssink”.
>
> I met a problem that the kmssink will have permission issue when 
> running with x11 and wayland. Because these two window system will 
> hold DRM-Master in their life time. So I’m change the code to use 
> control node “controlD64” for display and file node card0 for memory 
> management. It work really well. Video can show on multi display with 
> wayland and x11. But I notice that in the Linux kernel mainline, below 
> commit remove the control node:
>
> *commit 8a357d10043c75e980e7fcdb60d2b913491564af *
>
> *Author: Daniel Vetter <daniel.vetter at ffwll.ch 
> <mailto:daniel.vetter at ffwll.ch>>*
>
> *Date:   Fri Oct 28 10:10:50 2016 +0200 *
>
> **
>
> *    drm: Nerf DRM_CONTROL nodes *
>
> **
>
> *    Looking at the ioctl permission checks I noticed that it's 
> impossible *
>
> *    to import gem buffers into a control nodes, and fd2handle/handle2fd *
>
> *    also don't work, so no joy with dma-bufs. *
>
> **
>
> *    The only way to do anything with a control node is by drawing stuff *
>
> *    into a dumb buffer and displaying that. I suspect control nodes 
> are an *
>
> *    entirely unused thing, and a cursory check shows that there does 
> not *
>
> *    seem to be any callers of drmOpenControl nor of the other drmOpen *
>
> *    functions using DRM_MODE_CONTROL. *
>
> **
>
> *    Since I don't like dead uabi, let's remove it. But since this 
> would be *
>
> *    a really big change I think it's better to start out small by 
> simply *
>
> *    not registering anything. We can garbage-collect the dead code 
> later *
>
> *    on, once we're sure it's really not used anywhere. *
>
> **
>
> *    Acked-by: Dave Airlie <airlied at gmail.com <mailto:airlied at gmail.com>>*
>
> *    Signed-off-by: Daniel Vetter <daniel.vetter at intel.com 
> <mailto:daniel.vetter at intel.com>>*
>
> *    Link: 
> http://patchwork.freedesktop.org/patch/msgid/20161028081050.1042-1-daniel.vetter@ffwll.ch*
>
> This will have big impace on my case, and I cannot figure out how to 
> fix this issue. I think control node is useful, actually many users 
> are using this node for application development including rockchip and 
> amlogic. details please refer to: 
> http://gstreamer-devel.966125.n4.nabble.com/Can-kmssink-run-with-x11-or-wayland-which-is-based-on-drm-kms-also-td4683783.html#a4683819
>
> I‘m sending this mail for *require restoring control node in file 
> system, or is there any other way to fix my permission issue*?
>
> Thanks.
>
> Best wishes
>
> cid:image002.png at 01D13808.32F8E040*__*
>
> *Haihua Hu*
>
> *MPU Mulitmedia Software**__*
>
> NXP Semiconductors
>
> No.288 ZhuYuan Road
>
> Suzhou New District 215011, P.R.C
>
> Phone: +86-512-680566738
>
> jared.hu at nxp.com
>
> cid:image003.png at 01D13808.32F8E040
>
>
>
> _______________________________________________
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> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel


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