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

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Message-ID: <e191dc21-f92b-1e31-1999-3b653252d636@shipmail.org>
Date:   Sun, 19 Feb 2017 16:21:14 +0100
From:   Thomas Hellstrom <thomas@...pmail.org>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     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

So I think we need a quick revert of this commit or a quick stable
follow-up to unbreak things on our side.

/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)
>
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> dri-devel@...ts.freedesktop.org
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