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drm/i915/uapi: convert i915_user_extension to kernel doc 

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20210419105741.27844-3-matthew.auld@intel.com
This commit is contained in:
Matthew Auld 2021-04-19 11:57:40 +01:00
parent 2ef6a01fb6
commit 19d053d477
1 changed files with 50 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
include/uapi/drm/i915_drm.h
View File

@ -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];
};
/*