gbm: Export a per plane getter for offset

Unlike stride, there was no previous offset getter, so it can be right
on the first try.

v2: Return EINVAL when plane is greater than total planes to make it
match the similar APIs.
Avoid leak after fromPlanar (Daniel)
Make sure when getting offsets we consider dumb images (Daniel)

v3: Use Jason's recommendation for handling the non-planar case.

v4: Return int64_t so we can get real errors

v5: Add an assertion for dumb BOs (Jason)

Signed-off-by: Ben Widawsky <[email protected]>
Reviewed-by: Eric Engestrom <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Acked-by: Daniel Stone <[email protected]>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/gbm/main/gbm.c b/src/gbm/main/gbm.c
index 0a9f0bef7ee..afcca63da3a 100644
--- a/src/gbm/main/gbm.c
+++ b/src/gbm/main/gbm.c
@@ -194,6 +194,21 @@ gbm_bo_get_format(struct gbm_bo *bo)
    return bo->format;
 }
 
+/** Get the offset for the data of the specified plane
+ *
+ * Extra planes, and even the first plane, may have an offset from the start of
+ * the buffer object. This function will provide the offset for the given plane
+ * to be used in various KMS APIs.
+ *
+ * \param bo The buffer object
+ * \return The offset
+ */
+GBM_EXPORT int64_t
+gbm_bo_get_offset(struct gbm_bo *bo, int plane)
+{
+   return bo->gbm->bo_get_offset(bo, plane);
+}
+
 /** Get the gbm device used to create the buffer object
  *
  * \param bo The buffer object