Re: [RFC 1/3] component: alloc component_match without any comp to match

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Jul 11, 2018 at 07:41:26PM +0530, Ramalingam C wrote:
> If all the components associated to a component master is not added
> to the component framework due to the HW capability or Kconfig
> selection, component_match will be NULL at
> component_master_add_with_match().
> 
> To avoid this, component_match_alloc() is added to the framework,
> to allcoate the struct component_match with zero associated components.
> Hence component master can be added with a component_match with zero
> associated components.
> 
> This helps the component master bind call to get triggered always,
> even if no component is registered for that particular master.
> 
> This is useful if we use the component master for waiting for few
> components(features), only if they are registered, else proceed with
> the normal flow.

registered is a bit confusing here, I'd go with "supported by the
underlying hw". And maybe also explain that this is for big pci device
drivers where only some small/optional things are external components, so
different use-case from SoC drivers where the entire driver is always
built up from lots of small components.

When you submit this for real please also run script/get_maintainers.pl
for the full Cc: list.

> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Uh, don't do this, ever. I didn't put my s-o-b onto this patch. If you
want to credit me for the suggestion, use

Suggested-by: ...

s-o-b has legal meaning and is like signing a contract, you've just forged
my signature here. Same applies to reviewed-by tags btw.
-Daniel

> ---
>  drivers/base/component.c  | 30 ++++++++++++++++++++++++++++++
>  include/linux/component.h |  2 ++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/base/component.c b/drivers/base/component.c
> index 8946dfee4768..007fb738263a 100644
> --- a/drivers/base/component.c
> +++ b/drivers/base/component.c
> @@ -312,6 +312,36 @@ static int component_match_realloc(struct device *dev,
>  }
>  
>  /*
> + * Allocate the match without any component_match_array elements.
> + *
> + * This function is useful when the component master might end up
> + * registering itself without any matching components.
> + */
> +void component_match_alloc(struct device *master,
> +	struct component_match **matchptr)
> +{
> +	struct component_match *match = *matchptr;
> +
> +	if (IS_ERR(match))
> +		return;
> +
> +	if (match)
> +		return;
> +
> +	match = devres_alloc(devm_component_match_release,
> +			     sizeof(*match), GFP_KERNEL);
> +	if (!match) {
> +		*matchptr = ERR_PTR(-ENOMEM);
> +		return;
> +	}
> +
> +	devres_add(master, match);
> +
> +	*matchptr = match;
> +}
> +EXPORT_SYMBOL(component_match_alloc);
> +
> +/*
>   * Add a component to be matched, with a release function.
>   *
>   * The match array is first created or extended if necessary.
> diff --git a/include/linux/component.h b/include/linux/component.h
> index e71fbbbc74e2..3f6b420a58f8 100644
> --- a/include/linux/component.h
> +++ b/include/linux/component.h
> @@ -37,6 +37,8 @@ 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_alloc(struct device *master,
> +	struct component_match **matchptr);
>  
>  static inline void component_match_add(struct device *master,
>  	struct component_match **matchptr,
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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