drm/msm: extend the submit ioctl to pass in flags

We'll want to be able to pass in flags, such as asking for explicit
fencing, and possibly other things down the road.  Fortunately we
don't need a full 32b for the pipe-id.  So use the upper 16 bits
for flags (which could be extended or reduced later if needed, so
start adding flags from the high bits).

Since anything with the upper bits set would not be a valid pipe-id,
an old userspace would not set any of the upper bits, and an old
kernel would reject it as an invalid pipe-id.

Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem_submit.c

@@ -370,7 +370,10 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 	/* for now, we just have 3d pipe.. eventually this would need to
 	 * be more clever to dispatch to appropriate gpu module:
 	 */
-	if (args->pipe != MSM_PIPE_3D0)
+	if (MSM_PIPE_ID(args->flags) != MSM_PIPE_3D0)
+		return -EINVAL;
+
+	if (MSM_PIPE_FLAGS(args->flags) & ~MSM_SUBMIT_FLAGS)
 		return -EINVAL;
 
 	ret = mutex_lock_interruptible(&dev->struct_mutex);

include/uapi/drm/msm_drm.h

@@ -42,6 +42,15 @@ extern "C" {
 #define MSM_PIPE_2D1         0x02
 #define MSM_PIPE_3D0         0x10
 
+/* The pipe-id just uses the lower bits, so can be OR'd with flags in
+ * the upper 16 bits (which could be extended further, if needed, maybe
+ * we extend/overload the pipe-id some day to deal with multiple rings,
+ * but even then I don't think we need the full lower 16 bits).
+ */
+#define MSM_PIPE_ID_MASK     0xffff
+#define MSM_PIPE_ID(x)       ((x) & MSM_PIPE_ID_MASK)
+#define MSM_PIPE_FLAGS(x)    ((x) & ~MSM_PIPE_ID_MASK)
+
 /* timeouts are specified in clock-monotonic absolute times (to simplify
  * restarting interrupted ioctls).  The following struct is logically the
  * same as 'struct timespec' but 32/64b ABI safe.
@@ -175,12 +184,16 @@ struct drm_msm_gem_submit_bo {
 	__u64 presumed;       /* in/out, presumed buffer address */
 };
 
+/* Valid submit ioctl flags: */
+/* to start, nothing.. */
+#define MSM_SUBMIT_FLAGS 0
+
 /* Each cmdstream submit consists of a table of buffers involved, and
  * one or more cmdstream buffers.  This allows for conditional execution
  * (context-restore), and IB buffers needed for per tile/bin draw cmds.
  */
 struct drm_msm_gem_submit {
-	__u32 pipe;           /* in, MSM_PIPE_x */
+	__u32 flags;          /* MSM_PIPE_x | MSM_SUBMIT_x */
 	__u32 fence;          /* out */
 	__u32 nr_bos;         /* in, number of submit_bo's */
 	__u32 nr_cmds;        /* in, number of submit_cmd's */