drm/i915: Make the high dword offset more explicit in i915_reg_read_ioctl

Store the upper dword of the register offset in the whitelist as well.
This would allow it to read register where the two halves aren't sitting
right next to each other, and it'll make it easier to make register
access type safe.

While at it change the register offsets to u32 from u64. Our register
space isn't quite that big, yet :)

v2: Use ldw/udw as the suffixes, and add a note about
    64bit wide split regs (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446839021-18599-1-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 67cebe6d978f..67ef73a5d6eb 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1079,6 +1079,12 @@ struct drm_i915_gem_context_destroy {
 };
 
 struct drm_i915_reg_read {
+        /*
+         * Register offset.
+         * For 64bit wide registers where the upper 32bits don't immediately
+         * follow the lower 32bits, the offset of the lower 32bits must
+         * be specified
+         */
         __u64 offset;
         __u64 val; /* Return value */
 };