From 4d69c80e0d0fd8cf12d985841eb0fce5c29819ad Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Fri, 8 Feb 2019 00:27:56 +0100 Subject: component: Add documentation While typing these I think doing an s/component_master/aggregate/ would be useful: - it's shorter :-) - I think component/aggregate is much more meaningful naming than component/puppetmaster or something like that. At least to my English ear "aggregate" emphasizes much more the "assemble a pile of things into something bigger" aspect, and there's not really much of a control hierarchy between aggregate and constituing components. But that's way more than a quick doc typing exercise ... Thanks to Ram for commenting on an initial draft of these docs. v2: Review from Rafael: - git add Documenation/driver-api/component.rst - lots of polish to the wording + spelling fixes. v3: Review from Russell: - s/framework/helper - clarify the documentation for component_match_add functions. v4: Remove a few superflous "This". Reviewed-by: Rafael J. Wysocki Cc: "C, Ramalingam" Cc: Greg Kroah-Hartman Cc: Russell King Cc: Rafael J. Wysocki Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Rodrigo Vivi Cc: Jani Nikula Reviewed-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20190207232759.14553-1-daniel.vetter@ffwll.ch --- drivers/base/component.c | 106 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 103 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/base/component.c b/drivers/base/component.c index ddcea8739c12..1624c2a892a5 100644 --- a/drivers/base/component.c +++ b/drivers/base/component.c @@ -16,6 +16,32 @@ #include #include +/** + * DOC: overview + * + * The component helper allows drivers to collect a pile of sub-devices, + * including their bound drivers, into an aggregate driver. Various subsystems + * already provide functions to get hold of such components, e.g. + * of_clk_get_by_name(). The component helper can be used when such a + * subsystem-specific way to find a device is not available: The component + * helper fills the niche of aggregate drivers for specific hardware, where + * further standardization into a subsystem would not be practical. The common + * example is when a logical device (e.g. a DRM display driver) is spread around + * the SoC on various component (scanout engines, blending blocks, transcoders + * for various outputs and so on). + * + * The component helper also doesn't solve runtime dependencies, e.g. for system + * suspend and resume operations. See also :ref:`device links`. + * + * Components are registered using component_add() and unregistered with + * component_del(), usually from the driver's probe and disconnect functions. + * + * Aggregate drivers first assemble a component match list of what they need + * using component_match_add(). This is then registered as an aggregate driver + * using component_master_add_with_match(), and unregistered using + * component_master_del(). + */ + struct component; struct component_match_array { @@ -301,10 +327,24 @@ static int component_match_realloc(struct device *dev, return 0; } -/* - * Add a component to be matched, with a release function. +/** + * component_match_add_release - add a component match with release callback + * @master: device with the aggregate driver + * @matchptr: pointer to the list of component matches + * @release: release function for @compare_data + * @compare: compare function to match against all components + * @compare_data: opaque pointer passed to the @compare function + * + * Adds a new component match to the list stored in @matchptr, which the @master + * aggregate driver needs to function. The list of component matches pointed to + * by @matchptr must be initialized to NULL before adding the first match. + * + * The allocated match list in @matchptr is automatically released using devm + * actions, where upon @release will be called to free any references held by + * @compare_data, e.g. when @compare_data is a &device_node that must be + * released with of_node_put(). * - * The match array is first created or extended if necessary. + * See also component_match_add(). */ void component_match_add_release(struct device *master, struct component_match **matchptr, @@ -367,6 +407,18 @@ static void free_master(struct master *master) kfree(master); } +/** + * component_master_add_with_match - register an aggregate driver + * @dev: device with the aggregate driver + * @ops: callbacks for the aggregate driver + * @match: component match list for the aggregate driver + * + * Registers a new aggregate driver consisting of the components added to @match + * by calling one of the component_match_add() functions. Once all components in + * @match are available, it will be assembled by calling + * &component_master_ops.bind from @ops. Must be unregistered by calling + * component_master_del(). + */ int component_master_add_with_match(struct device *dev, const struct component_master_ops *ops, struct component_match *match) @@ -403,6 +455,15 @@ int component_master_add_with_match(struct device *dev, } EXPORT_SYMBOL_GPL(component_master_add_with_match); +/** + * component_master_del - unregister an aggregate driver + * @dev: device with the aggregate driver + * @ops: callbacks for the aggregate driver + * + * Unregisters an aggregate driver registered with + * component_master_add_with_match(). If necessary the aggregate driver is first + * disassembled by calling &component_master_ops.unbind from @ops. + */ void component_master_del(struct device *dev, const struct component_master_ops *ops) { @@ -430,6 +491,15 @@ static void component_unbind(struct component *component, devres_release_group(component->dev, component); } +/** + * component_unbind_all - unbind all component to an aggregate driver + * @master_dev: device with the aggregate driver + * @data: opaque pointer, passed to all components + * + * Unbinds all components to the aggregate @dev by passing @data to their + * &component_ops.unbind functions. Should be called from + * &component_master_ops.unbind. + */ void component_unbind_all(struct device *master_dev, void *data) { struct master *master; @@ -503,6 +573,15 @@ static int component_bind(struct component *component, struct master *master, return ret; } +/** + * component_bind_all - bind all component to an aggregate driver + * @master_dev: device with the aggregate driver + * @data: opaque pointer, passed to all components + * + * Binds all components to the aggregate @dev by passing @data to their + * &component_ops.bind functions. Should be called from + * &component_master_ops.bind. + */ int component_bind_all(struct device *master_dev, void *data) { struct master *master; @@ -537,6 +616,18 @@ int component_bind_all(struct device *master_dev, void *data) } EXPORT_SYMBOL_GPL(component_bind_all); +/** + * component_add - register a component + * @dev: component device + * @ops: component callbacks + * + * Register a new component for @dev. Functions in @ops will be called when the + * aggregate driver is ready to bind the overall driver by calling + * component_bind_all(). See also &struct component_ops. + * + * The component needs to be unregistered at driver unload/disconnect by calling + * component_del(). + */ int component_add(struct device *dev, const struct component_ops *ops) { struct component *component; @@ -568,6 +659,15 @@ int component_add(struct device *dev, const struct component_ops *ops) } EXPORT_SYMBOL_GPL(component_add); +/** + * component_del - unregister a component + * @dev: component device + * @ops: component callbacks + * + * Unregister a component added with component_add(). If the component is bound + * into an aggregate driver, this will force the entire aggregate driver, including + * all its components, to be unbound. + */ void component_del(struct device *dev, const struct component_ops *ops) { struct component *c, *component = NULL; -- cgit v1.2.3