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    Subject[PATCH 1/4] component: Add documentation
    Date
    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 <rafael.j.wysocki@intel.com>
    Cc: "C, Ramalingam" <ramalingam.c@intel.com>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Russell King <rmk+kernel@arm.linux.org.uk>
    Cc: Rafael J. Wysocki <rafael@kernel.org>
    Cc: Jaroslav Kysela <perex@perex.cz>
    Cc: Takashi Iwai <tiwai@suse.com>
    Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
    Cc: Jani Nikula <jani.nikula@linux.intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
    ---
    Documentation/driver-api/component.rst | 17 ++++
    Documentation/driver-api/device_link.rst | 3 +
    Documentation/driver-api/index.rst | 1 +
    drivers/base/component.c | 106 ++++++++++++++++++++++-
    include/linux/component.h | 70 +++++++++++++++
    5 files changed, 194 insertions(+), 3 deletions(-)
    create mode 100644 Documentation/driver-api/component.rst

    diff --git a/Documentation/driver-api/component.rst b/Documentation/driver-api/component.rst
    new file mode 100644
    index 000000000000..2da4a8f20607
    --- /dev/null
    +++ b/Documentation/driver-api/component.rst
    @@ -0,0 +1,17 @@
    +======================================
    +Component Helper for Aggregate Drivers
    +======================================
    +
    +.. kernel-doc:: drivers/base/component.c
    + :doc: overview
    +
    +
    +API
    +===
    +
    +.. kernel-doc:: include/linux/component.h
    + :internal:
    +
    +.. kernel-doc:: drivers/base/component.c
    + :export:
    +
    diff --git a/Documentation/driver-api/device_link.rst b/Documentation/driver-api/device_link.rst
    index d6763272e747..2d5919b2b337 100644
    --- a/Documentation/driver-api/device_link.rst
    +++ b/Documentation/driver-api/device_link.rst
    @@ -1,6 +1,9 @@
    .. |struct dev_pm_domain| replace:: :c:type:`struct dev_pm_domain <dev_pm_domain>`
    .. |struct generic_pm_domain| replace:: :c:type:`struct generic_pm_domain <generic_pm_domain>`

    +
    +.. _device_link:
    +
    ============
    Device links
    ============
    diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
    index ab38ced66a44..c0b600ed9961 100644
    --- a/Documentation/driver-api/index.rst
    +++ b/Documentation/driver-api/index.rst
    @@ -22,6 +22,7 @@ available subsections can be seen below.
    device_connection
    dma-buf
    device_link
    + component
    message-based
    sound
    frame-buffer
    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 <linux/slab.h>
    #include <linux/debugfs.h>

    +/**
    + * 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<device_link>`.
    + *
    + * 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;
    diff --git a/include/linux/component.h b/include/linux/component.h
    index e71fbbbc74e2..83da25bdf59c 100644
    --- a/include/linux/component.h
    +++ b/include/linux/component.h
    @@ -4,11 +4,31 @@

    #include <linux/stddef.h>

    +
    struct device;

    +/**
    + * struct component_ops - callbacks for component drivers
    + *
    + * Components are registered with component_add() and unregistered with
    + * component_del().
    + */
    struct component_ops {
    + /**
    + * @bind:
    + *
    + * Called through component_bind_all() when the aggregate driver is
    + * ready to bind the overall driver.
    + */
    int (*bind)(struct device *comp, struct device *master,
    void *master_data);
    + /**
    + * @unbind:
    + *
    + * Called through component_unbind_all() when the aggregate driver is
    + * ready to bind the overall driver, or when component_bind_all() fails
    + * part-ways through and needs to unbind some already bound components.
    + */
    void (*unbind)(struct device *comp, struct device *master,
    void *master_data);
    };
    @@ -21,8 +41,42 @@ void component_unbind_all(struct device *master, void *master_data);

    struct master;

    +/**
    + * struct component_master_ops - callback for the aggregate driver
    + *
    + * Aggregate drivers are registered with component_master_add_with_match() and
    + * unregistered with component_master_del().
    + */
    struct component_master_ops {
    + /**
    + * @bind:
    + *
    + * Called when all components or the aggregate driver, as specified in
    + * the match list passed to component_master_add_with_match(), are
    + * ready. Usually there are 3 steps to bind an aggregate driver:
    + *
    + * 1. Allocate a structure for the aggregate driver.
    + *
    + * 2. Bind all components to the aggregate driver by calling
    + * component_bind_all() with the aggregate driver structure as opaque
    + * pointer data.
    + *
    + * 3. Register the aggregate driver with the subsystem to publish its
    + * interfaces.
    + *
    + * Note that the lifetime of the aggregate driver does not align with
    + * any of the underlying &struct device instances. Therefore devm cannot
    + * be used and all resources acquired or allocated in this callback must
    + * be explicitly released in the @unbind callback.
    + */
    int (*bind)(struct device *master);
    + /**
    + * @unbind:
    + *
    + * Called when either the aggregate driver, using
    + * component_master_del(), or one of its components, using
    + * component_del(), is unregistered.
    + */
    void (*unbind)(struct device *master);
    };

    @@ -38,6 +92,22 @@ void component_match_add_release(struct device *master,
    void (*release)(struct device *, void *),
    int (*compare)(struct device *, void *), void *compare_data);

    +/**
    + * component_match_add - add a compent match
    + * @master: device with the aggregate driver
    + * @matchptr: pointer to the list of component matches
    + * @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.
    + *
    + * See also component_match_add_release().
    + */
    static inline void component_match_add(struct device *master,
    struct component_match **matchptr,
    int (*compare)(struct device *, void *), void *compare_data)
    --
    2.20.1
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