drm/msm: validate flags, etc

After reading a nice article on LWN[1], I went back and double checked
my handling of invalid-input checking.  Turns out there were a couple
places I had missed.

Since the driver is fairly young, and the devices it supports are really
only just barely usable for basic stuff (serial console) with an
upstream kernel, I think we should fix this now and revert specific
parts of this patch later in the unlikely event that a regression is
reported.

[1] https://lwn.net/Articles/588444/

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

include/uapi/drm/msm_drm.h

@@ -70,6 +70,12 @@ struct drm_msm_param {
 #define MSM_BO_WC            0x00020000
 #define MSM_BO_UNCACHED      0x00040000
 
+#define MSM_BO_FLAGS         (MSM_BO_SCANOUT | \
+                              MSM_BO_GPU_READONLY | \
+                              MSM_BO_CACHED | \
+                              MSM_BO_WC | \
+                              MSM_BO_UNCACHED)
+
 struct drm_msm_gem_new {
 	uint64_t size;           /* in */
 	uint32_t flags;          /* in, mask of MSM_BO_x */
@@ -86,6 +92,8 @@ struct drm_msm_gem_info {
 #define MSM_PREP_WRITE       0x02
 #define MSM_PREP_NOSYNC      0x04
 
+#define MSM_PREP_FLAGS       (MSM_PREP_READ | MSM_PREP_WRITE | MSM_PREP_NOSYNC)
+
 struct drm_msm_gem_cpu_prep {
 	uint32_t handle;         /* in */
 	uint32_t op;             /* in, mask of MSM_PREP_x */
@@ -153,6 +161,9 @@ struct drm_msm_gem_submit_cmd {
  */
 #define MSM_SUBMIT_BO_READ             0x0001
 #define MSM_SUBMIT_BO_WRITE            0x0002
+
+#define MSM_SUBMIT_BO_FLAGS            (MSM_SUBMIT_BO_READ | MSM_SUBMIT_BO_WRITE)
+
 struct drm_msm_gem_submit_bo {
 	uint32_t flags;          /* in, mask of MSM_SUBMIT_BO_x */
 	uint32_t handle;         /* in, GEM handle */