[PATCH 08/11] drm: Enforce unlocked ioctl operation for kms driver ioctls

[Daniel Vetter]

With the prep patches for i915 all kms drivers either have
DRM_UNLOCKED on all their ioctls. Or the ioctl always directly returns
with an invariant return value when in modeset mode. But that's only
the case for i915 and radeon. The drm core ioctls are unfortunately
too much a mess still to dare this.

Follow-up patches will remove DRM_UNLOCKED from all kms drivers to
prove that this is indeed the case.

Also update the documentation.

Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 Documentation/DocBook/drm.tmpl | 4 +++-
 drivers/gpu/drm/drm_ioctl.c    | 6 +++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index cfb43203a6a7..55dc106686df 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3747,7 +3747,9 @@ int num_ioctls;</synopsis>
 	    </para></listitem>
             <listitem><para>
 	      DRM_UNLOCKED - The ioctl handler will be called without locking
-	      the DRM global mutex
+	      the DRM global mutex. This is the enforced default for kms drivers
+	      (i.e. using the DRIVER_MODESET flag) and hence shouldn't be used
+	      any more for new drivers.
 	    </para></listitem>
 	  </itemizedlist>
 	</para>
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 75df8ea87cd7..a5a4aa89b1b4 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -728,6 +728,7 @@ long drm_ioctl(struct file *filp,
 	}
 
 	retcode = drm_ioctl_permit(ioctl->flags, file_priv);
+
 	if (unlikely(retcode))
 		goto err_i1;
 
@@ -755,7 +756,10 @@ long drm_ioctl(struct file *filp,
 		memset(kdata, 0, usize);
 	}
 
-	if (ioctl->flags & DRM_UNLOCKED)
+	/* Enforce sane locking for kms driver ioctls. Core ioctls are
+	 * too messy still. */
+	if (drm_core_check_feature(dev, DRIVER_MODESET) ||
+	    (ioctl->flags & DRM_UNLOCKED))
 		retcode = func(dev, kdata, file_priv);
 	else {
 		mutex_lock(&drm_global_mutex);
-- 
2.5.1