linux-kernel - Re: [PATCH v5] fpga: region: add owner module and take its refcount

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Message-ID: <e5f15ea4-f8e4-4a97-95f6-63a2099d084c@redhat.com>
Date: Mon, 15 Apr 2024 19:11:03 +0200
From: Marco Pagani <marpagan@...hat.com>
To: Xu Yilun <yilun.xu@...ux.intel.com>
Cc: Moritz Fischer <mdf@...nel.org>, Wu Hao <hao.wu@...el.com>,
 Xu Yilun <yilun.xu@...el.com>, Tom Rix <trix@...hat.com>,
 Jonathan Corbet <corbet@....net>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Alan Tull <atull@...nsource.altera.com>, Russ Weight
 <russ.weight@...ux.dev>, linux-fpga@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] fpga: region: add owner module and take its refcount

On 2024-04-15 14:19, Marco Pagani wrote:
> 
> 
> On 2024-04-13 04:35, Xu Yilun wrote:
>>>  /**
>>> - * fpga_region_register_full - create and register an FPGA Region device
>>> + * __fpga_region_register_full - create and register an FPGA Region device
>>>   * @parent: device parent
>>>   * @info: parameters for FPGA Region
>>> + * @owner: owner module containing the get_bridges function
>>
>> This is too specific and easily get unaligned if we add another
>> callback. How about "module containing the region ops"?
> 
> I had some concerns about using the name "region ops" in the kernel-doc
> comment since it was not supported by a struct definition nor referenced
> in the documentation. However, since the name is now referred to in the
> ops_owner pointer, making the change makes sense to me.
> 

On second thought, I think it would be better to leave the @owner
description to "module containing the get_bridges function" for the
moment. Otherwise, it could confuse the user by blurring the connection
between the @owner and @get_bridges parameters.

* __fpga_region_register - create and register an FPGA Region device
* [...]
* @get_bridges: optional function to get bridges to a list
* @owner: owner module containing get_bridges function

We can always modify the @owner description later, together with all the
necessary changes to add a new op, like grouping all ops in a structure
and changing the registration function signature.

Thanks,
Marco

> 
>>
>>>   *
>>>   * Return: struct fpga_region or ERR_PTR()
>>>   */
>>>  struct fpga_region *
>>> -fpga_region_register_full(struct device *parent, const struct fpga_region_info *info)
>>> +__fpga_region_register_full(struct device *parent, const struct fpga_region_info *info,
>>> +			    struct module *owner)
>>>  {
>>>  	struct fpga_region *region;
>>>  	int id, ret = 0;
>>> @@ -213,6 +215,7 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>>>  	region->compat_id = info->compat_id;
>>>  	region->priv = info->priv;
>>>  	region->get_bridges = info->get_bridges;
>>> +	region->ops_owner = owner;
>>>  
>>>  	mutex_init(&region->mutex);
>>>  	INIT_LIST_HEAD(&region->bridge_list);
>>> @@ -241,13 +244,14 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>>>  
>>>  	return ERR_PTR(ret);
>>>  }
>>> -EXPORT_SYMBOL_GPL(fpga_region_register_full);
>>> +EXPORT_SYMBOL_GPL(__fpga_region_register_full);
>>>  
>>>  /**
>>> - * fpga_region_register - create and register an FPGA Region device
>>> + * __fpga_region_register - create and register an FPGA Region device
>>>   * @parent: device parent
>>>   * @mgr: manager that programs this region
>>>   * @get_bridges: optional function to get bridges to a list
>>> + * @owner: owner module containing get_bridges function
>>
>> ditto
>>
>>>   *
>>>   * This simple version of the register function should be sufficient for most users.
>>>   * The fpga_region_register_full() function is available for users that need to
>>> @@ -256,17 +260,17 @@ EXPORT_SYMBOL_GPL(fpga_region_register_full);
>>>   * Return: struct fpga_region or ERR_PTR()
>>>   */
>>>  struct fpga_region *
>>> -fpga_region_register(struct device *parent, struct fpga_manager *mgr,
>>> -		     int (*get_bridges)(struct fpga_region *))
>>> +__fpga_region_register(struct device *parent, struct fpga_manager *mgr,
>>> +		       int (*get_bridges)(struct fpga_region *), struct module *owner)
>>>  {
>>>  	struct fpga_region_info info = { 0 };
>>>  
>>>  	info.mgr = mgr;
>>>  	info.get_bridges = get_bridges;
>>>  
>>> -	return fpga_region_register_full(parent, &info);
>>> +	return __fpga_region_register_full(parent, &info, owner);
>>>  }
>>> -EXPORT_SYMBOL_GPL(fpga_region_register);
>>> +EXPORT_SYMBOL_GPL(__fpga_region_register);
>>>  
>>>  /**
>>>   * fpga_region_unregister - unregister an FPGA region
>>> diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
>>> index 9d4d32909340..5fbc05fe70a6 100644
>>> --- a/include/linux/fpga/fpga-region.h
>>> +++ b/include/linux/fpga/fpga-region.h
>>> @@ -36,6 +36,7 @@ struct fpga_region_info {
>>>   * @mgr: FPGA manager
>>>   * @info: FPGA image info
>>>   * @compat_id: FPGA region id for compatibility check.
>>> + * @ops_owner: module containing the get_bridges function
>>
>> ditto
>>
>> Thanks,
>> Yilun
>>
>>>   * @priv: private data
>>>   * @get_bridges: optional function to get bridges to a list
>>>   */
>>> @@ -46,6 +47,7 @@ struct fpga_region {
>>>  	struct fpga_manager *mgr;
>>>  	struct fpga_image_info *info;
>>>  	struct fpga_compat_id *compat_id;
>>> +	struct module *ops_owner;
>>>  	void *priv;
>>>  	int (*get_bridges)(struct fpga_region *region);
>>>  };
>>