linux-kernel - Re: [PATCH v3 2/7] reset: mpfs: use the auxiliary device creation helper

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Message-ID: <1jv7tczytk.fsf@starbuckisacylon.baylibre.com>
Date: Fri, 14 Feb 2025 09:59:35 +0100
From: Jerome Brunet <jbrunet@...libre.com>
To: Conor Dooley <conor@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,  Dave Ertman
 <david.m.ertman@...el.com>,  Ira Weiny <ira.weiny@...el.com>,  "Rafael J.
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 Bergmann <arnd@...db.de>,  Danilo Krummrich <dakr@...nel.org>,  Conor
 Dooley <conor.dooley@...rochip.com>,  Daire McNamara
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Subject: Re: [PATCH v3 2/7] reset: mpfs: use the auxiliary device creation
 helper

On Thu 13 Feb 2025 at 17:59, Conor Dooley <conor@...nel.org> wrote:

> On Tue, Feb 11, 2025 at 06:27:59PM +0100, Jerome Brunet wrote:
>> The auxiliary device creation of this driver is simple enough to
>> use the available auxiliary device creation helper.
>> 
>> Use it and remove some boilerplate code.
>> 
>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>> ---
>>  drivers/reset/reset-mpfs.c | 52 +++-------------------------------------------
>>  1 file changed, 3 insertions(+), 49 deletions(-)
>> 
>> diff --git a/drivers/reset/reset-mpfs.c b/drivers/reset/reset-mpfs.c
>> index 574e59db83a4fcf30b60cb5f638607a2ec7b0580..bbea64862181877eb7ae51fdaa9e50ffac17c908 100644
>> --- a/drivers/reset/reset-mpfs.c
>> +++ b/drivers/reset/reset-mpfs.c
>> @@ -155,62 +155,16 @@ static int mpfs_reset_probe(struct auxiliary_device *adev,
>>  	return devm_reset_controller_register(dev, rcdev);
>>  }
>>  
>> -static void mpfs_reset_unregister_adev(void *_adev)
>> -{
>> -	struct auxiliary_device *adev = _adev;
>> -
>> -	auxiliary_device_delete(adev);
>> -	auxiliary_device_uninit(adev);
>> -}
>> -
>> -static void mpfs_reset_adev_release(struct device *dev)
>> -{
>> -	struct auxiliary_device *adev = to_auxiliary_dev(dev);
>> -
>> -	kfree(adev);
>> -}
>> -
>> -static struct auxiliary_device *mpfs_reset_adev_alloc(struct device *clk_dev)
>> -{
>> -	struct auxiliary_device *adev;
>> -	int ret;
>> -
>> -	adev = kzalloc(sizeof(*adev), GFP_KERNEL);
>> -	if (!adev)
>> -		return ERR_PTR(-ENOMEM);
>> -
>> -	adev->name = "reset-mpfs";
>> -	adev->dev.parent = clk_dev;
>> -	adev->dev.release = mpfs_reset_adev_release;
>> -	adev->id = 666u;
>> -
>> -	ret = auxiliary_device_init(adev);
>> -	if (ret) {
>> -		kfree(adev);
>> -		return ERR_PTR(ret);
>> -	}
>> -
>> -	return adev;
>> -}
>> -
>>  int mpfs_reset_controller_register(struct device *clk_dev, void __iomem *base)
>>  {
>>  	struct auxiliary_device *adev;
>> -	int ret;
>>  
>> -	adev = mpfs_reset_adev_alloc(clk_dev);
>> +	adev = devm_auxiliary_device_create(clk_dev, "reset-mpfs",
>> +					    (__force void *)base, 666u);
>
> Moving the boilerplate into a helper makes sense:
> Acked-by: Conor Dooley <conor.dooley@...rochip.com>
>
> One think that's always felt a bit meh to me is this id number stuff,
> I just threw in 666 for meme value.

:)

> The whole thing seems super
> arbitrary, do any of the users of this helper actually put meaningful
> values into the id parameter?

In example changes I've sent, no.

In other simple usages (those using container_of()) of the auxiliary
bus, I think there are a few that uses 0 and 1 for 2 instances.

I guess your question is "do we really need this parameter here ?"

We could remove it and still address 90% of the original target.

Keeping it leaves the door open in case the figure above does not hold
and it is pretty cheap to do. It could also enable drivers requiring an
IDA to use the helper, possibly.

>
>>  	if (IS_ERR(adev))
>>  		return PTR_ERR(adev);
>>  
>> -	ret = auxiliary_device_add(adev);
>> -	if (ret) {
>> -		auxiliary_device_uninit(adev);
>> -		return ret;
>> -	}
>> -
>> -	adev->dev.platform_data = (__force void *)base;
>> -
>> -	return devm_add_action_or_reset(clk_dev, mpfs_reset_unregister_adev, adev);
>> +	return 0;
>>  }
>>  EXPORT_SYMBOL_NS_GPL(mpfs_reset_controller_register, "MCHP_CLK_MPFS");
>>  
>> 
>> -- 
>> 2.45.2
>> 

-- 
Jerome