linux-kernel - Re: [PATCH] irqdomain: Add documentation for irq_create_of

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Date:   Sat, 19 Dec 2020 22:34:07 +0100
From:   Marion & Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Marc Zyngier <maz@...nel.org>
Cc:     tglx@...utronix.de, mripard@...nel.org, dan.carpenter@...cle.com,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] irqdomain: Add documentation for irq_create_of_mapping()


Le 18/12/2020 à 19:59, Marc Zyngier a écrit :
> Hi Christophe,
>
> On Tue, 15 Dec 2020 20:07:47 +0000,
> Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:
>> Add a description for 'irq_create_of_mapping()' and make explicit the fact
>> that the resources allocated by this function can be freed by calling
>> 'irq_dispose_mapping()' when needed (i.e. error handling path, remove
>> function, ...)
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>> The wording can certainly be improved.
>>
>> My goal is only to make clear if patches such as:
>>     https://lore.kernel.org/lkml/20201214202117.146293-1-christophe.jaillet@wanadoo.fr/
>> are needed or not.
>> ---
>>   kernel/irq/irqdomain.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
>> index 6aacd342cd14..d761ece8d43e 100644
>> --- a/kernel/irq/irqdomain.c
>> +++ b/kernel/irq/irqdomain.c
>> @@ -858,6 +858,15 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
>>   }
>>   EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);
>>   
>> +/**
>> + * irq_create_of_mapping() - Map an interrupt
> I think this deserves a bit more work. My immediate questions when
> reading this are "map where? and to what?".

I won't be of great help here.
I don't know this code enough to be able to provide an accurate description.

>> + * @irq_data: structure of_phandle_args returned by a previous
>> + * of_irq_parse_xxx() call
> That's not strictly true. A of_phandle_args structure can be created
> from scratch (and numerous drivers do that).
>
>> + *
>> + * The resources allocated by this function should be freed by
>> + * calling irq_dispose_mapping() when the mapping if not useful
>> + * anymore.
> This really is a bit of documentation for irq_dispose_mapping(), isn't it?

Well, I don't agree.

I think it is easier to see that some resources need to be freed with a 
dedicated function if it is explained in the description of the function 
which allocates the resource.

CJ

>
>> + */
>>   unsigned int irq_create_of_mapping(struct of_phandle_args *irq_data)
>>   {
>>   	struct irq_fwspec fwspec;
> Thanks,
>
> 	M.
>