Some basic stuff about tag support is explained under doc/devlop/driver-model.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- doc/develop/driver-model/design.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/doc/develop/driver-model/design.rst b/doc/develop/driver-model/design.rst index b0e6337030a1..3e88dc40e6fd 100644 --- a/doc/develop/driver-model/design.rst +++ b/doc/develop/driver-model/design.rst @@ -1042,6 +1042,26 @@ data structure might be worthwhile in some rare cases, once we understand what the bottlenecks are.
+Tag Support +----------- + +It is sometimes useful for a subsystem to associate its own private +data (or object) to a DM device, i.e. struct udevice, to support +additional features. + +Tag support in driver model will give us the ability to do so dynamically +instead of modifying "udevice" data structure. In the initial release, we +will support two type of attributes: +- a pointer with dm_tag_set_ptr(), and +- an unsigned long with dm_tag_set_val() + +For example, UEFI subsystem utilizes the feature to maintain efi_disk +objects depending on linked udevice's lifecycle. + +While the current implementation is quite simple, it will get evolved +as the feature is more extensively used in U-Boot subsystems. + + Changes since v1 ----------------