[Intel-gfx] [PATCH v2 3/4] drm/i915/uapi: convert i915_user_extension to kernel doc

Matthew Auld
2021-04-19T10:59:12Z

Add some example usage for the extension chaining also, which is quite
nifty.

v2: (Daniel)
- clarify that the name is just some integer, also document that the
name space is not global
v3: prefer kernel-doc references for structs

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Dave Airlie <airlied@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: mesa-dev@lists.freedesktop.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
---
include/uapi/drm/i915_drm.h | 54 ++++++++++++++++++++++++++++++++++---
1 file changed, 50 insertions(+), 4 deletions(-)

diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 92da48e935d1..e2867d8cd5e3 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -62,8 +62,8 @@ extern "C" {
#define I915_ERROR_UEVENT "ERROR"
#define I915_RESET_UEVENT "RESET"

-/*
- * i915_user_extension: Base class for defining a chain of extensions
+/**
+ * struct i915_user_extension - Base class for defining a chain of extensions
*
* Many interfaces need to grow over time. In most cases we can simply
* extend the struct and have userspace pass in more data. Another option,
@@ -76,12 +76,58 @@ extern "C" {
* increasing complexity, and for large parts of that interface to be
* entirely optional. The downside is more pointer chasing; chasing across
* the __user boundary with pointers encapsulated inside u64.
+ *
+ * Example chaining:
+ *
+ * .. code-block:: C
+ *
+ * struct i915_user_extension ext3 {
+ * .next_extension = 0, // end
+ * .name = ...,
+ * };
+ * struct i915_user_extension ext2 {
+ * .next_extension = (uintptr_t)&ext3,
+ * .name = ...,
+ * };
+ * struct i915_user_extension ext1 {
+ * .next_extension = (uintptr_t)&ext2,
+ * .name = ...,
+ * };
+ *
+ * Typically the struct i915_user_extension would be embedded in some uAPI
+ * struct, and in this case we would feed it the head of the chain(i.e ext1),
+ * which would then apply all of the above extensions.
+ *
*/
struct i915_user_extension {
+ /**
+ * @next_extension:
+ *
+ * Pointer to the next struct i915_user_extension, or zero if the end.
+ */
__u64 next_extension;
+ /**
+ * @name: Name of the extension.
+ *
+ * Note that the name here is just some integer.
+ *
+ * Also note that the name space for this is not global for the whole
+ * driver, but rather its scope/meaning is limited to the specific piece
+ * of uAPI which has embedded the struct i915_user_extension.
+ */
__u32 name;
- __u32 flags; /* All undefined bits must be zero. */
- __u32 rsvd[4]; /* Reserved for future use; must be zero. */
+ /**
+ * @flags: MBZ
+ *
+ * All undefined bits must be zero.
+ */
+ __u32 flags;
+ /**
+ * @rsvd: MBZ
+ *
+ * Reserved for future use; must be zero.
+ */
+ __u32 rsvd[4];
};

/*