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

Daniel Vetter daniel.vetter at ffwll.ch
Thu May 15 06:00:08 PDT 2014

Leftover from the old days of ums and should be used any longer. Since

commit 29935554b384b1b3a7377d6f0b03b21d18a61683
Author: Laurent Pinchart <laurent.pinchart at 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.

v2: Fix up mangled sentence spotted by Michel.

Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Michel Dänzer <michel at daenzer.net>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
 Documentation/DocBook/drm.tmpl | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 83dd0b043c28..96cee6438472 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -2861,12 +2861,12 @@ int num_ioctls;</synopsis>
-                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 counter is reset to 0 at some point during modeset. Modern
+		drivers should not call this any more since with kernel mode
+		setting it is a no-op.

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