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Date:   Fri, 8 Feb 2019 16:36:34 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ramalingam C <ramalingam.c@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>
Subject: Re: [PATCH 2/4] components: multiple components for a device

On Fri, Feb 8, 2019 at 4:23 PM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Fri, Feb 08, 2019 at 10:28:49AM +0000, Russell King - ARM Linux admin wrote:
> > On Fri, Feb 08, 2019 at 12:27:57AM +0100, Daniel Vetter wrote:
> > > Component framework is extended to support multiple components for
> > > a struct device. These will be matched with different masters based on
> > > its sub component value.
> > >
> > > We are introducing this, as I915 needs two different components
> > > with different subcomponent value, which will be matched to two
> > > different component masters(Audio and HDCP) based on the subcomponent
> > > values.
> > >
> > > v2: Add documenation.
> > >
> > > v3: Rebase on top of updated documenation.
> > >
> > > v4: Review from Rafael:
> > > - Remove redundant "This" from kerneldoc (also in the previous patch)
> > > - Streamline the logic in find_component() a bit.
> > >
> > > Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch> (v1 code)
> > > Signed-off-by: Ramalingam C <ramalingam.c@...el.com> (v1 commit message)
> > > Cc: Ramalingam C <ramalingam.c@...el.com>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Cc: Russell King <rmk+kernel@....linux.org.uk>
> > > Cc: Rafael J. Wysocki <rafael@...nel.org>
> > > Cc: Jaroslav Kysela <perex@...ex.cz>
> > > Cc: Takashi Iwai <tiwai@...e.com>
> > > Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
> > > Cc: Jani Nikula <jani.nikula@...ux.intel.com>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
> > > ---
> > >  drivers/base/component.c  | 158 +++++++++++++++++++++++++++++---------
> > >  include/linux/component.h |  10 ++-
> > >  2 files changed, 129 insertions(+), 39 deletions(-)
> > >
> > > diff --git a/drivers/base/component.c b/drivers/base/component.c
> > > index 1624c2a892a5..7dbc41cccd58 100644
> > > --- a/drivers/base/component.c
> > > +++ b/drivers/base/component.c
> > > @@ -47,6 +47,7 @@ struct component;
> > >  struct component_match_array {
> > >     void *data;
> > >     int (*compare)(struct device *, void *);
> > > +   int (*compare_typed)(struct device *, int, void *);
> > >     void (*release)(struct device *, void *);
> > >     struct component *component;
> > >     bool duplicate;
> > > @@ -74,6 +75,7 @@ struct component {
> > >     bool bound;
> > >
> > >     const struct component_ops *ops;
> > > +   int subcomponent;
> > >     struct device *dev;
> > >  };
> > >
> > > @@ -158,7 +160,7 @@ static struct master *__master_find(struct device *dev,
> > >  }
> > >
> > >  static struct component *find_component(struct master *master,
> > > -   int (*compare)(struct device *, void *), void *compare_data)
> > > +   struct component_match_array *mc)
> > >  {
> > >     struct component *c;
> > >
> > > @@ -166,7 +168,11 @@ static struct component *find_component(struct master *master,
> > >             if (c->master && c->master != master)
> > >                     continue;
> > >
> > > -           if (compare(c->dev, compare_data))
> > > +           if (mc->compare && mc->compare(c->dev, mc->data))
> > > +                   return c;
> > > +
> > > +           if (mc->compare_typed &&
> > > +               mc->compare_typed(c->dev, c->subcomponent, mc->data))
> > >                     return c;
> > >     }
> > >
> > > @@ -192,7 +198,7 @@ static int find_components(struct master *master)
> > >             if (match->compare[i].component)
> > >                     continue;
> > >
> > > -           c = find_component(master, mc->compare, mc->data);
> > > +           c = find_component(master, mc);
> > >             if (!c) {
> > >                     ret = -ENXIO;
> > >                     break;
> > > @@ -327,29 +333,12 @@ static int component_match_realloc(struct device *dev,
> > >     return 0;
> > >  }
> > >
> > > -/**
> > > - * 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().
> > > - *
> > > - * See also component_match_add().
> > > - */
> > > -void component_match_add_release(struct device *master,
> > > +static void __component_match_add(struct device *master,
> > >     struct component_match **matchptr,
> > >     void (*release)(struct device *, void *),
> > > -   int (*compare)(struct device *, void *), void *compare_data)
> > > +   int (*compare)(struct device *, void *),
> > > +   int (*compare_typed)(struct device *, int, void *),
> > > +   void *compare_data)
> > >  {
> > >     struct component_match *match = *matchptr;
> > >
> > > @@ -381,13 +370,69 @@ void component_match_add_release(struct device *master,
> > >     }
> > >
> > >     match->compare[match->num].compare = compare;
> > > +   match->compare[match->num].compare_typed = compare_typed;
> > >     match->compare[match->num].release = release;
> > >     match->compare[match->num].data = compare_data;
> > >     match->compare[match->num].component = NULL;
> > >     match->num++;
> > >  }
> > > +
> > > +/**
> > > + * 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. This
> > > + * only matches against components added with component_add().
> > > + *
> > > + * 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().
> > > + *
> > > + * See also component_match_add() and component_match_add_typed().
> > > + */
> > > +void component_match_add_release(struct device *master,
> > > +   struct component_match **matchptr,
> > > +   void (*release)(struct device *, void *),
> > > +   int (*compare)(struct device *, void *), void *compare_data)
> > > +{
> > > +   __component_match_add(master, matchptr, release, compare, NULL,
> > > +                         compare_data);
> > > +}
> > >  EXPORT_SYMBOL(component_match_add_release);
> > >
> > > +/**
> > > + * component_match_add_typed - add a compent match for a typed component
> > > + * @master: device with the aggregate driver
> > > + * @matchptr: pointer to the list of component matches
> > > + * @compare_typed: compare function to match against all typed 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. This
> > > + * only matches against components added with component_add_typed().
> > > + *
> > > + * The allocated match list in @matchptr is automatically released using devm
> > > + * actions.
> > > + *
> > > + * See also component_match_add_release() and component_match_add_typed().
> > > + */
> > > +void component_match_add_typed(struct device *master,
> > > +   struct component_match **matchptr,
> > > +   int (*compare_typed)(struct device *, int, void *), void *compare_data)
> > > +{
> > > +   __component_match_add(master, matchptr, NULL, NULL, compare_typed,
> > > +                         compare_data);
> >
> > You're still passing some compare data in that may need to be released,
> > but you are explicitly denying the ability to provide a release
> > function pointer here.  What was the reasoning behind that decision?
> > If someone wanted to use this with compare_data being a device_node,
> > how should that be handled?
>
> Same way we've handled it originally, adding the new variant. I'm not a
> huge fan of adding api preemptively, without a user. And the data pointer
> we pass around in i915 for mei_hdcp and snd-hda-intel don't hold
> references (we don't even use them, we just compare the device against
> hardcoded expectations). Since the new compare_typed is entirely
> orthogonal to whether you have a release function or not, that should be
> simple to do.

Forgot to add: I also don't expect a user for this. The ->release
callback is used for dt drivers, because of_node_put(). And well
designed device tree will not have multiple components stack in very
awkward ways on the exact same underlying device, that would simply be
rather unclean DT design. x86 otoh, thanks to window's "one pci
device, one driver" expectation is full of that kind of
kludged-together SoC-but-not-really behind one pci device. Therefore I
expect the overlap for this kind of stuff to be 0.

This includes all the hand-rolled hacks we have in i915 that predate
component, e.g. ips on ironlake or the pmu serialization on vlv. So
with a 4/4 rate of possible users of component_typed not needed a
->release callback I think not providing that combo for now is the
right call. And as mentioned, really easy to adjust in case I've
guessed wrong here.
-Daniel

> > > +}
> > > +EXPORT_SYMBOL(component_match_add_typed);
> > > +
> > >  static void free_master(struct master *master)
> > >  {
> > >     struct component_match *match = master->match;
> > > @@ -616,19 +661,8 @@ 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)
> > > +static int __component_add(struct device *dev, const struct component_ops *ops,
> > > +   int subcomponent)
> > >  {
> > >     struct component *component;
> > >     int ret;
> > > @@ -639,6 +673,7 @@ int component_add(struct device *dev, const struct component_ops *ops)
> > >
> > >     component->ops = ops;
> > >     component->dev = dev;
> > > +   component->subcomponent = subcomponent;
> > >
> > >     dev_dbg(dev, "adding component (ops %ps)\n", ops);
> > >
> > > @@ -657,6 +692,55 @@ int component_add(struct device *dev, const struct component_ops *ops)
> > >
> > >     return ret < 0 ? ret : 0;
> > >  }
> > > +
> > > +/**
> > > + * component_add_typed - register a component
> > > + * @dev: component device
> > > + * @ops: component callbacks
> > > + * @subcomponent: nonzero identifier for subcomponents
> > > + *
> > > + * Register a new component for @dev. Functions in @ops will be call when the
> > > + * aggregate driver is ready to bind the overall driver by calling
> > > + * component_bind_all(). See also &struct component_ops.
> > > + *
> > > + * @subcomponent must be nonzero and is used to differentiate between multiple
> > > + * components registerd on the same device @dev. These components are match
> > > + * using component_match_add_typed().
> > > + *
> > > + * The component needs to be unregistered at driver unload/disconnect by
> > > + * calling component_del().
> > > + *
> > > + * See also component_add().
> > > + */
> > > +int component_add_typed(struct device *dev, const struct component_ops *ops,
> > > +   int subcomponent)
> > > +{
> > > +   if (WARN_ON(subcomponent == 0))
> > > +           return -EINVAL;
> > > +
> > > +   return __component_add(dev, ops, subcomponent);
> > > +}
> > > +EXPORT_SYMBOL_GPL(component_add_typed);
> > > +
> > > +/**
> > > + * 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().
> > > + *
> > > + * See also component_add_typed() for a variant that allows multipled different
> > > + * components on the same device.
> > > + */
> > > +int component_add(struct device *dev, const struct component_ops *ops)
> > > +{
> > > +   return __component_add(dev, ops, 0);
> > > +}
> > >  EXPORT_SYMBOL_GPL(component_add);
> > >
> > >  /**
> > > diff --git a/include/linux/component.h b/include/linux/component.h
> > > index 83da25bdf59c..30bcc7e590eb 100644
> > > --- a/include/linux/component.h
> > > +++ b/include/linux/component.h
> > > @@ -34,6 +34,8 @@ struct component_ops {
> > >  };
> > >
> > >  int component_add(struct device *, const struct component_ops *);
> > > +int component_add_typed(struct device *dev, const struct component_ops *ops,
> > > +   int subcomponent);
> > >  void component_del(struct device *, const struct component_ops *);
> > >
> > >  int component_bind_all(struct device *master, void *master_data);
> > > @@ -91,6 +93,9 @@ void component_match_add_release(struct device *master,
> > >     struct component_match **matchptr,
> > >     void (*release)(struct device *, void *),
> > >     int (*compare)(struct device *, void *), void *compare_data);
> > > +void component_match_add_typed(struct device *master,
> > > +   struct component_match **matchptr,
> > > +   int (*compare_typed)(struct device *, int, void *), void *compare_data);
> > >
> > >  /**
> > >   * component_match_add - add a compent match
> > > @@ -101,12 +106,13 @@ void component_match_add_release(struct device *master,
> > >   *
> > >   * 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.
> > > + * by @matchptr must be initialized to NULL before adding the first match. This
> > > + * only matches against components added with component_add().
> > >   *
> > >   * The allocated match list in @matchptr is automatically released using devm
> > >   * actions.
> > >   *
> > > - * See also component_match_add_release().
> > > + * See also component_match_add_release() and component_match_add_typed().
> > >   */
> > >  static inline void component_match_add(struct device *master,
> > >     struct component_match **matchptr,
> > > --
> > > 2.20.1
> > >
> > >
> >
> > --
> > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> > FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> > According to speedtest.net: 11.9Mbps down 500kbps up
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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