From 7a3c628c43f7200684edf81783e11b69fd0fd7df Mon Sep 17 00:00:00 2001 From: Simon Glass <sjg@chromium.org> Date: Sun, 24 Jan 2021 14:32:48 -0700 Subject: [PATCH] dm: core: Add documentation about device removal Make mention of this feature in the core documentation so people can discover it without looking at a header file. Signed-off-by: Simon Glass <sjg@chromium.org> --- doc/driver-model/design.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/doc/driver-model/design.rst b/doc/driver-model/design.rst index ffed7d5f79..2417976ab7 100644 --- a/doc/driver-model/design.rst +++ b/doc/driver-model/design.rst @@ -880,6 +880,26 @@ If a parent has children these will be destroyed first. After this point the device does not exist and its memory has be deallocated. +Special cases for removal +------------------------- + +Some devices need to do clean-up before the OS is called. For example, a USB +driver may want to stop the bus. This can be done in the remove() method. +Some special flags are used to determine whether to remove the device: + + DM_FLAG_OS_PREPARE - indicates that the device needs to get ready for OS + boot. The device will be removed just before the OS is booted + DM_REMOVE_ACTIVE_DMA - indicates that the device uses DMA. This is + effectively the same as DM_FLAG_OS_PREPARE, so the device is removed + before the OS is booted + DM_FLAG_VITAL - indicates that the device is 'vital' to the operation of + other devices. It is possible to remove this device after all regular + devices are removed. This is useful e.g. for a clock, which need to + be active during the device-removal phase. + +The dm_remove_devices_flags() function can be used to remove devices based on +their driver flags. + Data Structures --------------- -- 2.39.5