linux-kernel - Re: [PATCH] [RFC] drm: Nerf DRM_CONTROL nodes

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Date:   Mon, 20 Feb 2017 23:22:52 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     Thomas Hellstrom <thomas@...pmail.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Dave Airlie <airlied@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC] drm: Nerf DRM_CONTROL nodes

On Sun, Feb 19, 2017 at 4:21 PM, Thomas Hellstrom <thomas@...pmail.org> wrote:
> So I think we need a quick revert of this commit or a quick stable
> follow-up to unbreak things on our side.

I'd much prefer we just register control nodes for vmwgfx only, with a
commit message explaining in detail what exactly your control tool is
using (i.e. which ioctl), plus links to the source code for future
references. Also not sold on the immediate revert, this stuff has been
merged since months.
-Daniel

>
> /Thomas
>
>
> On 02/19/2017 03:54 PM, Thomas Hellstrom wrote:
>> Hi!
>>
>> This patch breaks the vmwgfx resolutionKMS daemon which opens a control
>> node to tell DRM about the monitor layout...
>>
>> /Thomas
>>
>>
>> On 10/28/2016 10:10 AM, Daniel Vetter wrote:
>>> 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.
>>>
>>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>>> ---
>>>  drivers/gpu/drm/drm_drv.c | 6 ------
>>>  1 file changed, 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>> index 6efdba4993fc..f085e28ffc6f 100644
>>> --- a/drivers/gpu/drm/drm_drv.c
>>> +++ b/drivers/gpu/drm/drm_drv.c
>>> @@ -517,12 +517,6 @@ int drm_dev_init(struct drm_device *dev,
>>>              goto err_free;
>>>      }
>>>
>>> -    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
>>> -            ret = drm_minor_alloc(dev, DRM_MINOR_CONTROL);
>>> -            if (ret)
>>> -                    goto err_minors;
>>> -    }
>>> -
>>>      if (drm_core_check_feature(dev, DRIVER_RENDER)) {
>>>              ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
>>>              if (ret)
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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