[Intel-gfx] [PATCH] 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.

v2: Really only do this for driver ioctls, spotted by David Herrmann.
And drop spurious whitespace change.

Cc: David Herrmann <dh.herrmann at gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 Documentation/DocBook/drm.tmpl |  4 +++-
 drivers/gpu/drm/drm_ioctl.c    | 10 ++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 8c654866e1a2..5395cde6905e 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 530c501422fd..8ce2a0c59116 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -691,13 +691,16 @@ long drm_ioctl(struct file *filp,
 	char stack_kdata[128];
 	char *kdata = NULL;
 	unsigned int usize, asize, drv_size;
+	bool is_driver_ioctl;
 
 	dev = file_priv->minor->dev;
 
 	if (drm_device_is_unplugged(dev))
 		return -ENODEV;
 
-	if (nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END) {
+	is_driver_ioctl = nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END;
+
+	if (is_driver_ioctl) {
 		/* driver ioctl */
 		if (nr - DRM_COMMAND_BASE >= dev->driver->num_ioctls)
 			goto err_i1;
@@ -756,7 +759,10 @@ 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) && is_driver_ioctl) ||
+	    (ioctl->flags & DRM_UNLOCKED))
 		retcode = func(dev, kdata, file_priv);
 	else {
 		mutex_lock(&drm_global_mutex);
-- 
2.5.1