Re: [PATCH 06/12] drm/doc: Discourage usage of MODESET_CTL ioctl

Michel Dänzer
2014-05-15T04:27:54Z

On 15.05.2014 03:51, Daniel Vetter wrote:
> Leftover from the old days of ums and should be used any longer. Since
>
> commit 29935554b384b1b3a7377d6f0b03b21d18a61683
> Author: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Date: Wed May 30 00:58:09 2012 +0200
>
> drm: Disallow DRM_IOCTL_MODESET_CTL for KMS drivers
>
> it is a complete no-Op for kms drivers.
>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> Documentation/DocBook/drm.tmpl | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
> index 83dd0b043c28..e37a77a72b8b 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -2861,12 +2861,11 @@ int num_ioctls;</synopsis>
> <term>DRM_IOCTL_MODESET_CTL</term>
>
>
> - This should be called by application level drivers before and
> - after mode setting, since on many devices the vertical blank
> - counter is reset at that time. Internally, the DRM snapshots
> - the last vblank count when the ioctl is called with the
> - _DRM_PRE_MODESET command, so that the counter won't go backwards
> - (which is dealt with when _DRM_POST_MODESET is used).
> + This was only used for user-mode-settind drivers around
> + modesetting changes to allow the kernel to update the vblank
> + interrupt after mode setting, since on many devices the vertical
> + blank.

This sentence looks mangled pretty badly. Did you have something like
this in mind?

"This was only used for user-mode-setting drivers around modesetting
changes to allow the kernel to keep the vertical blank counters
consistent, since on many devices the hardware vertical blank counter is
reset to 0 at some point during modeset changes."

--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer