drm/i915: Document and reject invalid tiling modes

Through the GTT interface to the fence registers, we can only handle
linear, X and Y tiling. The more esoteric tiling patterns are ignored.
Document that the tiling ABI only supports upto Y tiling, and reject any
attempts to set a tiling mode other than NONE, X or Y.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-17-git-send-email-chris@chris-wilson.co.uk

2 files changed, 4 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index c0e01333bddf..6817f69947d9 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -68,6 +68,9 @@ i915_tiling_ok(struct drm_device *dev, int stride, int size, int tiling_mode)
         if (tiling_mode == I915_TILING_NONE)
                 return true;
 
+        if (tiling_mode > I915_TILING_LAST)
+                return false;
+
         if (IS_GEN2(dev) ||
             (tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev)))
                 tile_width = 128;
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 0f292733cffc..452629de7a57 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -926,6 +926,7 @@ struct drm_i915_gem_caching {
 #define I915_TILING_NONE        0
 #define I915_TILING_X           1
 #define I915_TILING_Y           2
+#define I915_TILING_LAST        I915_TILING_Y
 
 #define I915_BIT_6_SWIZZLE_NONE         0
 #define I915_BIT_6_SWIZZLE_9            1