Date:   Sat, 9 Oct 2021 16:16:50 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Russ Weight <russell.h.weight@...el.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        hao.wu@...el.com, matthew.gerlach@...el.com
Subject: Re: [PATCH v12 3/3] fpga: region: Use standard dev_release for class
 driver

On Tue, Sep 14, 2021 at 02:43:27PM -0700, Russ Weight wrote:
> The FPGA region class driver data structure is being treated as a
> managed resource instead of using the standard dev_release call-back
> function to release the class data structure. This change removes the
> managed resource code and combines the create() and register()
> functions into a single register() or register_full() function.
> 
> The register_full() function accepts an info data structure to provide
> flexibility in passing optional parameters. The register() function
> supports the current parameter list for users that don't require the
> use of optional parameters.
> 
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> Reviewed-by: Xu Yilun <yilun.xu@...el.com>

Acked-by: Xu Yilun <yilun.xu@...el.com>

> ---
> v12:
>   - No change
> v11:
>   - Rebased to latest linux-next (no conflicts)
> v10:
>   - Fixed commit message to reference register_full() instead of
>     register_simple().
>   - Updated documentation to reference the fpga_region_info structure
> v9:
>   - Cleaned up documentation for the FPGA Region register functions
>   - Renamed fpga_region_register() to fpga_region_register_full()
>   - Renamed fpga_region_register_simple() to fpga_region_register()
> v8:
>   - Added reviewed-by tag.
>   - Updated Documentation/driver-api/fpga/fpga-region.rst documentation.
> v7:
>   - Update the commit message to describe the new parameters for the
>     fpga_region_register() function and to mention the
>     fpga_region_register_simple() function.
>   - Fix function prototypes in header file to rename dev to parent.
>   - Some cleanup of comments.
>   - Update function definitions/prototypes to apply const to the new info
>     parameter.
>   - Verify a non-null info pointer in the register() functions.
> v6:
>   - Moved FPGA manager optional parameters out of the ops structure and
>     back into the FPGA Region structure.
>   - Changed fpga_region_register() parameters to accept an info data
>     structure to provide flexibility in passing optional parameters.
>   - Added fpga_region_register_simple() functions to support current
>     parameters for users that don't require the use of optional parameters.
> v5:
>   - Rebased on top of recently accepted patches.
>   - Created the fpga_region_ops data structure which is optionally passed
>     to fpga_region_register(). compat_id, the get_bridges() pointer, and
>     the priv pointer are included in the fpga_region_ops structure.
> v4:
>   - Added the compat_id parameter to fpga_region_register() to ensure
>     that the compat_id is set before the device_register() call.
>   - Modified the dfl_fpga_feature_devs_enumerate() function to restore
>     the fpga_region_register() call to the correct location.
> v3:
>   - Cleaned up comment header for fpga_region_register()
>   - Fix fpga_region_register() error return on ida_simple_get() failure
> v2:
>   - No changes
> ---
>  Documentation/driver-api/fpga/fpga-region.rst |  12 +-
>  drivers/fpga/dfl-fme-region.c                 |  17 ++-
>  drivers/fpga/dfl.c                            |  12 +-
>  drivers/fpga/fpga-region.c                    | 119 +++++++-----------
>  drivers/fpga/of-fpga-region.c                 |  10 +-
>  include/linux/fpga/fpga-region.h              |  36 ++++--
>  6 files changed, 95 insertions(+), 111 deletions(-)
> 
> diff --git a/Documentation/driver-api/fpga/fpga-region.rst b/Documentation/driver-api/fpga/fpga-region.rst
> index 2636a27c11b2..dc55d60a0b4a 100644
> --- a/Documentation/driver-api/fpga/fpga-region.rst
> +++ b/Documentation/driver-api/fpga/fpga-region.rst
> @@ -46,8 +46,11 @@ API to add a new FPGA region
>  ----------------------------
>  
>  * struct fpga_region - The FPGA region struct
> -* devm_fpga_region_create() - Allocate and init a region struct
> -* fpga_region_register() -  Register an FPGA region
> +* struct fpga_region_info - Parameter structure for fpga_region_register_full()
> +* fpga_region_register_full() -  Create and register an FPGA region using the
> +  fpga_region_info structure to provide the full flexibility of options
> +* fpga_region_register() -  Create and register an FPGA region using standard
> +  arguments
>  * fpga_region_unregister() -  Unregister an FPGA region
>  
>  The FPGA region's probe function will need to get a reference to the FPGA
> @@ -75,8 +78,11 @@ following APIs to handle building or tearing down that list.
>  .. kernel-doc:: include/linux/fpga/fpga-region.h
>     :functions: fpga_region
>  
> +.. kernel-doc:: include/linux/fpga/fpga-region.h
> +   :functions: fpga_region_info
> +
>  .. kernel-doc:: drivers/fpga/fpga-region.c
> -   :functions: devm_fpga_region_create
> +   :functions: fpga_region_register_full
>  
>  .. kernel-doc:: drivers/fpga/fpga-region.c
>     :functions: fpga_region_register
> diff --git a/drivers/fpga/dfl-fme-region.c b/drivers/fpga/dfl-fme-region.c
> index 1eeb42af1012..4aebde0a7f1c 100644
> --- a/drivers/fpga/dfl-fme-region.c
> +++ b/drivers/fpga/dfl-fme-region.c
> @@ -30,6 +30,7 @@ static int fme_region_get_bridges(struct fpga_region *region)
>  static int fme_region_probe(struct platform_device *pdev)
>  {
>  	struct dfl_fme_region_pdata *pdata = dev_get_platdata(&pdev->dev);
> +	struct fpga_region_info info = { 0 };
>  	struct device *dev = &pdev->dev;
>  	struct fpga_region *region;
>  	struct fpga_manager *mgr;
> @@ -39,20 +40,18 @@ static int fme_region_probe(struct platform_device *pdev)
>  	if (IS_ERR(mgr))
>  		return -EPROBE_DEFER;
>  
> -	region = devm_fpga_region_create(dev, mgr, fme_region_get_bridges);
> -	if (!region) {
> -		ret = -ENOMEM;
> +	info.mgr = mgr;
> +	info.compat_id = mgr->compat_id;
> +	info.get_bridges = fme_region_get_bridges;
> +	info.priv = pdata;
> +	region = fpga_region_register_full(dev, &info);
> +	if (IS_ERR(region)) {
> +		ret = PTR_ERR(region);
>  		goto eprobe_mgr_put;
>  	}
>  
> -	region->priv = pdata;
> -	region->compat_id = mgr->compat_id;
>  	platform_set_drvdata(pdev, region);
>  
> -	ret = fpga_region_register(region);
> -	if (ret)
> -		goto eprobe_mgr_put;
> -
>  	dev_dbg(dev, "DFL FME FPGA Region probed\n");
>  
>  	return 0;
> diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> index c99b78ee008a..1f2ad1c309f7 100644
> --- a/drivers/fpga/dfl.c
> +++ b/drivers/fpga/dfl.c
> @@ -1405,19 +1405,15 @@ dfl_fpga_feature_devs_enumerate(struct dfl_fpga_enum_info *info)
>  	if (!cdev)
>  		return ERR_PTR(-ENOMEM);
>  
> -	cdev->region = devm_fpga_region_create(info->dev, NULL, NULL);
> -	if (!cdev->region) {
> -		ret = -ENOMEM;
> -		goto free_cdev_exit;
> -	}
> -
>  	cdev->parent = info->dev;
>  	mutex_init(&cdev->lock);
>  	INIT_LIST_HEAD(&cdev->port_dev_list);
>  
> -	ret = fpga_region_register(cdev->region);
> -	if (ret)
> +	cdev->region = fpga_region_register(info->dev, NULL, NULL);
> +	if (IS_ERR(cdev->region)) {
> +		ret = PTR_ERR(cdev->region);
>  		goto free_cdev_exit;
> +	}
>  
>  	/* create and init build info for enumeration */
>  	binfo = devm_kzalloc(info->dev, sizeof(*binfo), GFP_KERNEL);
> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> index a4838715221f..b0ac18de4885 100644
> --- a/drivers/fpga/fpga-region.c
> +++ b/drivers/fpga/fpga-region.c
> @@ -180,39 +180,42 @@ static struct attribute *fpga_region_attrs[] = {
>  ATTRIBUTE_GROUPS(fpga_region);
>  
>  /**
> - * fpga_region_create - alloc and init a struct fpga_region
> + * fpga_region_register_full - 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
> - *
> - * The caller of this function is responsible for freeing the resulting region
> - * struct with fpga_region_free().  Using devm_fpga_region_create() instead is
> - * recommended.
> + * @info: parameters for FPGA Region
>   *
> - * Return: struct fpga_region or NULL
> + * Return: struct fpga_region or ERR_PTR()
>   */
> -struct fpga_region
> -*fpga_region_create(struct device *parent,
> -		    struct fpga_manager *mgr,
> -		    int (*get_bridges)(struct fpga_region *))
> +struct fpga_region *
> +fpga_region_register_full(struct device *parent, const struct fpga_region_info *info)
>  {
>  	struct fpga_region *region;
>  	int id, ret = 0;
>  
> +	if (!info) {
> +		dev_err(parent,
> +			"Attempt to register without required info structure\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
>  	region = kzalloc(sizeof(*region), GFP_KERNEL);
>  	if (!region)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>  
>  	id = ida_simple_get(&fpga_region_ida, 0, 0, GFP_KERNEL);
> -	if (id < 0)
> +	if (id < 0) {
> +		ret = id;
>  		goto err_free;
> +	}
> +
> +	region->mgr = info->mgr;
> +	region->compat_id = info->compat_id;
> +	region->priv = info->priv;
> +	region->get_bridges = info->get_bridges;
>  
> -	region->mgr = mgr;
> -	region->get_bridges = get_bridges;
>  	mutex_init(&region->mutex);
>  	INIT_LIST_HEAD(&region->bridge_list);
>  
> -	device_initialize(&region->dev);
>  	region->dev.class = fpga_region_class;
>  	region->dev.parent = parent;
>  	region->dev.of_node = parent->of_node;
> @@ -222,6 +225,12 @@ struct fpga_region
>  	if (ret)
>  		goto err_remove;
>  
> +	ret = device_register(&region->dev);
> +	if (ret) {
> +		put_device(&region->dev);
> +		return ERR_PTR(ret);
> +	}
> +
>  	return region;
>  
>  err_remove:
> @@ -229,76 +238,32 @@ struct fpga_region
>  err_free:
>  	kfree(region);
>  
> -	return NULL;
> -}
> -EXPORT_SYMBOL_GPL(fpga_region_create);
> -
> -/**
> - * fpga_region_free - free an FPGA region created by fpga_region_create()
> - * @region: FPGA region
> - */
> -void fpga_region_free(struct fpga_region *region)
> -{
> -	ida_simple_remove(&fpga_region_ida, region->dev.id);
> -	kfree(region);
> -}
> -EXPORT_SYMBOL_GPL(fpga_region_free);
> -
> -static void devm_fpga_region_release(struct device *dev, void *res)
> -{
> -	struct fpga_region *region = *(struct fpga_region **)res;
> -
> -	fpga_region_free(region);
> +	return ERR_PTR(ret);
>  }
> +EXPORT_SYMBOL_GPL(fpga_region_register_full);
>  
>  /**
> - * devm_fpga_region_create - create and initialize a managed FPGA region struct
> + * 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
>   *
> - * This function is intended for use in an FPGA region driver's probe function.
> - * After the region driver creates the region struct with
> - * devm_fpga_region_create(), it should register it with fpga_region_register().
> - * The region driver's remove function should call fpga_region_unregister().
> - * The region struct allocated with this function will be freed automatically on
> - * driver detach.  This includes the case of a probe function returning error
> - * before calling fpga_region_register(), the struct will still get cleaned up.
> + * 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
> + * pass additional, optional parameters.
>   *
> - * Return: struct fpga_region or NULL
> + * Return: struct fpga_region or ERR_PTR()
>   */
> -struct fpga_region
> -*devm_fpga_region_create(struct device *parent,
> -			 struct fpga_manager *mgr,
> -			 int (*get_bridges)(struct fpga_region *))
> +struct fpga_region *
> +fpga_region_register(struct device *parent, struct fpga_manager *mgr,
> +		     int (*get_bridges)(struct fpga_region *))
>  {
> -	struct fpga_region **ptr, *region;
> -
> -	ptr = devres_alloc(devm_fpga_region_release, sizeof(*ptr), GFP_KERNEL);
> -	if (!ptr)
> -		return NULL;
> +	struct fpga_region_info info = { 0 };
>  
> -	region = fpga_region_create(parent, mgr, get_bridges);
> -	if (!region) {
> -		devres_free(ptr);
> -	} else {
> -		*ptr = region;
> -		devres_add(parent, ptr);
> -	}
> +	info.mgr = mgr;
> +	info.get_bridges = get_bridges;
>  
> -	return region;
> -}
> -EXPORT_SYMBOL_GPL(devm_fpga_region_create);
> -
> -/**
> - * fpga_region_register - register an FPGA region
> - * @region: FPGA region
> - *
> - * Return: 0 or -errno
> - */
> -int fpga_region_register(struct fpga_region *region)
> -{
> -	return device_add(&region->dev);
> +	return fpga_region_register_full(parent, &info);
>  }
>  EXPORT_SYMBOL_GPL(fpga_region_register);
>  
> @@ -316,6 +281,10 @@ EXPORT_SYMBOL_GPL(fpga_region_unregister);
>  
>  static void fpga_region_dev_release(struct device *dev)
>  {
> +	struct fpga_region *region = to_fpga_region(dev);
> +
> +	ida_simple_remove(&fpga_region_ida, region->dev.id);
> +	kfree(region);
>  }
>  
>  /**
> diff --git a/drivers/fpga/of-fpga-region.c b/drivers/fpga/of-fpga-region.c
> index e3c25576b6b9..9c662db1c508 100644
> --- a/drivers/fpga/of-fpga-region.c
> +++ b/drivers/fpga/of-fpga-region.c
> @@ -405,16 +405,12 @@ static int of_fpga_region_probe(struct platform_device *pdev)
>  	if (IS_ERR(mgr))
>  		return -EPROBE_DEFER;
>  
> -	region = devm_fpga_region_create(dev, mgr, of_fpga_region_get_bridges);
> -	if (!region) {
> -		ret = -ENOMEM;
> +	region = fpga_region_register(dev, mgr, of_fpga_region_get_bridges);
> +	if (IS_ERR(region)) {
> +		ret = PTR_ERR(region);
>  		goto eprobe_mgr_put;
>  	}
>  
> -	ret = fpga_region_register(region);
> -	if (ret)
> -		goto eprobe_mgr_put;
> -
>  	of_platform_populate(np, fpga_region_of_match, NULL, &region->dev);
>  	platform_set_drvdata(pdev, region);
>  
> diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
> index 27cb706275db..3b87f232425c 100644
> --- a/include/linux/fpga/fpga-region.h
> +++ b/include/linux/fpga/fpga-region.h
> @@ -7,6 +7,27 @@
>  #include <linux/fpga/fpga-mgr.h>
>  #include <linux/fpga/fpga-bridge.h>
>  
> +struct fpga_region;
> +
> +/**
> + * struct fpga_region_info - collection of parameters an FPGA Region
> + * @mgr: fpga region manager
> + * @compat_id: FPGA region id for compatibility check.
> + * @priv: fpga region private data
> + * @get_bridges: optional function to get bridges to a list
> + *
> + * fpga_region_info contains parameters for the register_full function.
> + * These are separated into an info structure because they some are optional
> + * others could be added to in the future. The info structure facilitates
> + * maintaining a stable API.
> + */
> +struct fpga_region_info {
> +	struct fpga_manager *mgr;
> +	struct fpga_compat_id *compat_id;
> +	void *priv;
> +	int (*get_bridges)(struct fpga_region *region);
> +};
> +
>  /**
>   * struct fpga_region - FPGA Region structure
>   * @dev: FPGA Region device
> @@ -37,15 +58,12 @@ struct fpga_region *fpga_region_class_find(
>  
>  int fpga_region_program_fpga(struct fpga_region *region);
>  
> -struct fpga_region
> -*fpga_region_create(struct device *dev, struct fpga_manager *mgr,
> -		    int (*get_bridges)(struct fpga_region *));
> -void fpga_region_free(struct fpga_region *region);
> -int fpga_region_register(struct fpga_region *region);
> -void fpga_region_unregister(struct fpga_region *region);
> +struct fpga_region *
> +fpga_region_register_full(struct device *parent, const struct fpga_region_info *info);
>  
> -struct fpga_region
> -*devm_fpga_region_create(struct device *dev, struct fpga_manager *mgr,
> -			int (*get_bridges)(struct fpga_region *));
> +struct fpga_region *
> +fpga_region_register(struct device *parent, struct fpga_manager *mgr,
> +		     int (*get_bridges)(struct fpga_region *));
> +void fpga_region_unregister(struct fpga_region *region);
>  
>  #endif /* _FPGA_REGION_H */
> -- 
> 2.25.1

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