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

[Ramalingam C <ramalingam.c@intel.com>]

On Thursday 12 July 2018 01:51 PM, Daniel Vetter wrote:
> 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.
sure.
>
>> 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.

Since the idea is suggested by you, thought that its my responsibility
to give the credit. Sure got your point.

I will add Suggested-by: instead.

Thanks,
Ram.

> -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
>>

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