Re: [PATCH v9 2/3] fpga: bridge: Use standard dev_release for class driver

[Tom Rix <trix@xxxxxxxxxx>]

Russ,

Similar concern with 2 register functions as in fpga-mgr.

But here it does not seen that any instance uses 
fpga_bridge_register_full directly.

So it really isn't needed.

However if fpga-mgr changes to having a single register(... *info), 
fpga-bridge should likewise.

Peeking ahead, fpga-region looks similar.

my preference for api stability is for have mgr,bridge and region to 
have the *register_full(... *info) as the only *register()


On 6/30/21 6:37 PM, Russ Weight wrote:
> The FPGA bridge 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_simple() function.
>
> The register() function accepts an info data structure to provide
> flexibility in passing optional parameters. The register_simple()
> 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@xxxxxxxxx>
> Reviewed-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> ---
> v9:
>    - Cleaned up documentation for the FPGA Bridge register functions
>    - Renamed fpga_bridge_register() to fpga_bridge_register_full()
>    - Renamed fpga_bridge_register_simple() to fpga_bridge_register()
> v8:
>    - Added reviewed-by tag.
>    - Updated Documentation/driver-api/fpga/fpga-bridge.rst documentation.
> v7:
>    - Update the commit message to describe the new parameters for the
>      fpga_bridge_register() function and to mention the
>      fpga_bridge_register_simple() function.
>    - Fix function prototypes in header file to rename dev to parent.
>    - Some cleanup of comments.
>    - Update function defintions/prototypes to apply const to the new info
>      parameter.
>    - Verify that info->br_ops is non-null in register functions.
> v6:
>    - Changed fpga_bridge_register() parameters to accept an info data
>      structure to provide flexibility in passing optional parameters.
>    - Added fpga_bridge_register_simple() function to support current
>      parameters for users that don't require the use of optional
>      parameters.
> v5:
>    - Rebased on top of recently accepted patches.
> v4:
>    - Restore the previous format for the Return value in the comment header
>      for fpga_bridge_register()
> v3:
>    - Cleaned up comment header for fpga_bridge_register()
>    - Fix error return values for fpga_bridge_register()
> v2:
>    - No changes
> ---
>   Documentation/driver-api/fpga/fpga-bridge.rst |   8 +-
>   drivers/fpga/altera-fpga2sdram.c              |  12 +-
>   drivers/fpga/altera-freeze-bridge.c           |  10 +-
>   drivers/fpga/altera-hps2fpga.c                |  12 +-
>   drivers/fpga/dfl-fme-br.c                     |  10 +-
>   drivers/fpga/fpga-bridge.c                    | 137 ++++++------------
>   drivers/fpga/xilinx-pr-decoupler.c            |  17 +--
>   include/linux/fpga/fpga-bridge.h              |  33 +++--
>   8 files changed, 101 insertions(+), 138 deletions(-)
>
> diff --git a/Documentation/driver-api/fpga/fpga-bridge.rst b/Documentation/driver-api/fpga/fpga-bridge.rst
> index 8d650b4e2ce6..38e3bac8e877 100644
> --- a/Documentation/driver-api/fpga/fpga-bridge.rst
> +++ b/Documentation/driver-api/fpga/fpga-bridge.rst
> @@ -6,8 +6,10 @@ API to implement a new FPGA bridge
>   
>   * struct fpga_bridge - The FPGA Bridge structure
>   * struct fpga_bridge_ops - Low level Bridge driver ops
> -* devm_fpga_bridge_create() - Allocate and init a bridge struct
> -* fpga_bridge_register() - Register a bridge
> +* fpga_bridge_register_full() - Create and register a bridge using the
> +  fpga_bridge_info structure to provide the full flexibility of options
fpga_bridge_info (and fpga_mgr_info earlier) could be added to the 
kernel-doc:: list lower down
> +* fpga_bridge_register() - Create and register a bridge using standard
> +  arguments
>   * fpga_bridge_unregister() - Unregister a bridge
>   
>   .. kernel-doc:: include/linux/fpga/fpga-bridge.h
> @@ -17,7 +19,7 @@ API to implement a new FPGA bridge
>      :functions: fpga_bridge_ops
>   
>   .. kernel-doc:: drivers/fpga/fpga-bridge.c
> -   :functions: devm_fpga_bridge_create
> +   :functions: fpga_bridge_register_full
>   
>   .. kernel-doc:: drivers/fpga/fpga-bridge.c
>      :functions: fpga_bridge_register
> diff --git a/drivers/fpga/altera-fpga2sdram.c b/drivers/fpga/altera-fpga2sdram.c
> index a78e49c63c64..66063507116b 100644
> --- a/drivers/fpga/altera-fpga2sdram.c
> +++ b/drivers/fpga/altera-fpga2sdram.c
> @@ -121,17 +121,13 @@ static int alt_fpga_bridge_probe(struct platform_device *pdev)
>   	/* Get f2s bridge configuration saved in handoff register */
>   	regmap_read(sysmgr, SYSMGR_ISWGRP_HANDOFF3, &priv->mask);
>   
> -	br = devm_fpga_bridge_create(dev, F2S_BRIDGE_NAME,
> -				     &altera_fpga2sdram_br_ops, priv);
> -	if (!br)
> -		return -ENOMEM;
> +	br = fpga_bridge_register(dev, F2S_BRIDGE_NAME,
> +				  &altera_fpga2sdram_br_ops, priv);
> +	if (IS_ERR(br))
> +		return PTR_ERR(mgr);
>   
>   	platform_set_drvdata(pdev, br);
>   
> -	ret = fpga_bridge_register(br);
> -	if (ret)
> -		return ret;
> -
>   	dev_info(dev, "driver initialized with handoff %08x\n", priv->mask);
>   
>   	if (!of_property_read_u32(dev->of_node, "bridge-enable", &enable)) {
> diff --git a/drivers/fpga/altera-freeze-bridge.c b/drivers/fpga/altera-freeze-bridge.c
> index dd58c4aea92e..bfbfa43cd05b 100644
> --- a/drivers/fpga/altera-freeze-bridge.c
> +++ b/drivers/fpga/altera-freeze-bridge.c
> @@ -244,14 +244,14 @@ static int altera_freeze_br_probe(struct platform_device *pdev)
>   
>   	priv->base_addr = base_addr;
>   
> -	br = devm_fpga_bridge_create(dev, FREEZE_BRIDGE_NAME,
> -				     &altera_freeze_br_br_ops, priv);
> -	if (!br)
> -		return -ENOMEM;
> +	br = fpga_bridge_register(dev, FREEZE_BRIDGE_NAME,
> +				  &altera_freeze_br_br_ops, priv);
> +	if (IS_ERR(br))
> +		return PTR_ERR(br);
>   
>   	platform_set_drvdata(pdev, br);
>   
> -	return fpga_bridge_register(br);
> +	return 0;
>   }
>   
>   static int altera_freeze_br_remove(struct platform_device *pdev)
> diff --git a/drivers/fpga/altera-hps2fpga.c b/drivers/fpga/altera-hps2fpga.c
> index 77b95f251821..aa758426c22b 100644
> --- a/drivers/fpga/altera-hps2fpga.c
> +++ b/drivers/fpga/altera-hps2fpga.c
> @@ -180,19 +180,15 @@ static int alt_fpga_bridge_probe(struct platform_device *pdev)
>   		}
>   	}
>   
> -	br = devm_fpga_bridge_create(dev, priv->name,
> -				     &altera_hps2fpga_br_ops, priv);
> -	if (!br) {
> -		ret = -ENOMEM;
> +	br = fpga_bridge_register(dev, priv->name,
> +				  &altera_hps2fpga_br_ops, priv);
> +	if (IS_ERR(br)) {
> +		ret = PTR_ERR(br);
>   		goto err;
>   	}
>   
>   	platform_set_drvdata(pdev, br);
>   
> -	ret = fpga_bridge_register(br);
> -	if (ret)
> -		goto err;
> -
>   	return 0;
>   
>   err:
> diff --git a/drivers/fpga/dfl-fme-br.c b/drivers/fpga/dfl-fme-br.c
> index 3ff9f3a687ce..808d1f4d76df 100644
> --- a/drivers/fpga/dfl-fme-br.c
> +++ b/drivers/fpga/dfl-fme-br.c
> @@ -68,14 +68,14 @@ static int fme_br_probe(struct platform_device *pdev)
>   
>   	priv->pdata = dev_get_platdata(dev);
>   
> -	br = devm_fpga_bridge_create(dev, "DFL FPGA FME Bridge",
> -				     &fme_bridge_ops, priv);
> -	if (!br)
> -		return -ENOMEM;
> +	br = fpga_bridge_register(dev, "DFL FPGA FME Bridge",
> +				  &fme_bridge_ops, priv);
> +	if (IS_ERR(br))
> +		return PTR_ERR(br);
>   
>   	platform_set_drvdata(pdev, br);
>   
> -	return fpga_bridge_register(br);
> +	return 0;
>   }
>   
>   static int fme_br_remove(struct platform_device *pdev)
> diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
> index 798f55670646..e6d98be8531b 100644
> --- a/drivers/fpga/fpga-bridge.c
> +++ b/drivers/fpga/fpga-bridge.c
> @@ -312,55 +312,63 @@ static struct attribute *fpga_bridge_attrs[] = {
>   ATTRIBUTE_GROUPS(fpga_bridge);
>   
>   /**
> - * fpga_bridge_create - create and initialize a struct fpga_bridge
> + * fpga_bridge_register_full - create and register an FPGA Bridge device
>    * @parent:	FPGA bridge device from pdev
> - * @name:	FPGA bridge name
> - * @br_ops:	pointer to structure of fpga bridge ops
> - * @priv:	FPGA bridge private data
> + * @info:	parameters for FPGA Bridge
>    *
> - * The caller of this function is responsible for freeing the bridge with
> - * fpga_bridge_free().  Using devm_fpga_bridge_create() instead is recommended.
> - *
> - * Return: struct fpga_bridge or NULL
> + * Return: struct fpga_bridge pointer or ERR_PTR()
>    */
> -struct fpga_bridge *fpga_bridge_create(struct device *parent, const char *name,
> -				       const struct fpga_bridge_ops *br_ops,
> -				       void *priv)
> +struct fpga_bridge *
> +fpga_bridge_register_full(struct device *parent,
> +			  const struct fpga_bridge_info *info)
>   {
>   	struct fpga_bridge *bridge;
>   	int id, ret;
>   
> -	if (!name || !strlen(name)) {
> +	if (!info->br_ops) {
> +		dev_err(parent, "Attempt to register without fpga_bridge_ops\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	if (!info->name || !strlen(info->name)) {
>   		dev_err(parent, "Attempt to register with no name!\n");
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>   	}
>   
>   	bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
>   	if (!bridge)
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>   
>   	id = ida_simple_get(&fpga_bridge_ida, 0, 0, GFP_KERNEL);
> -	if (id < 0)
> +	if (id < 0) {
> +		ret = id;
>   		goto error_kfree;
> +	}
>   
>   	mutex_init(&bridge->mutex);
>   	INIT_LIST_HEAD(&bridge->node);
>   
> -	bridge->name = name;
> -	bridge->br_ops = br_ops;
> -	bridge->priv = priv;
> +	bridge->name = info->name;
> +	bridge->br_ops = info->br_ops;
> +	bridge->priv = info->priv;
>   
> -	device_initialize(&bridge->dev);
> -	bridge->dev.groups = br_ops->groups;
> +	bridge->dev.groups = info->br_ops->groups;
>   	bridge->dev.class = fpga_bridge_class;
>   	bridge->dev.parent = parent;
>   	bridge->dev.of_node = parent->of_node;
>   	bridge->dev.id = id;
> +	of_platform_populate(bridge->dev.of_node, NULL, NULL, &bridge->dev);
>   
>   	ret = dev_set_name(&bridge->dev, "br%d", id);
>   	if (ret)
>   		goto error_device;
>   
> +	ret = device_register(&bridge->dev);
> +	if (ret) {
> +		put_device(&bridge->dev);
> +		return ERR_PTR(ret);
> +	}
> +
>   	return bridge;
>   
>   error_device:
> @@ -368,88 +376,35 @@ struct fpga_bridge *fpga_bridge_create(struct device *parent, const char *name,
>   error_kfree:
>   	kfree(bridge);
>   
> -	return NULL;
> -}
> -EXPORT_SYMBOL_GPL(fpga_bridge_create);
> -
> -/**
> - * fpga_bridge_free - free an fpga bridge created by fpga_bridge_create()
> - * @bridge:	FPGA bridge struct
> - */
> -void fpga_bridge_free(struct fpga_bridge *bridge)
> -{
> -	ida_simple_remove(&fpga_bridge_ida, bridge->dev.id);
> -	kfree(bridge);
> -}
> -EXPORT_SYMBOL_GPL(fpga_bridge_free);
> -
> -static void devm_fpga_bridge_release(struct device *dev, void *res)
> -{
> -	struct fpga_bridge *bridge = *(struct fpga_bridge **)res;
> -
> -	fpga_bridge_free(bridge);
> +	return ERR_PTR(ret);
>   }
> +EXPORT_SYMBOL_GPL(fpga_bridge_register_full);
>   
>   /**
> - * devm_fpga_bridge_create - create and init a managed struct fpga_bridge
> + * fpga_bridge_register - create and register an FPGA Bridge device
>    * @parent:	FPGA bridge device from pdev
>    * @name:	FPGA bridge name
>    * @br_ops:	pointer to structure of fpga bridge ops
>    * @priv:	FPGA bridge private data
>    *
> - * This function is intended for use in an FPGA bridge driver's probe function.
> - * After the bridge driver creates the struct with devm_fpga_bridge_create(), it
> - * should register the bridge with fpga_bridge_register().  The bridge driver's
> - * remove function should call fpga_bridge_unregister().  The bridge 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_bridge_register(), the struct will still get cleaned up.
> + * This simple version of the register should be sufficient for most users.
> + * The fpga_bridge_register_full() function is available for users that need to pass
> + * additional, optional parameters.
>    *
> - *  Return: struct fpga_bridge or NULL
> + * Return: struct fpga_bridge pointer or ERR_PTR()
>    */
> -struct fpga_bridge
> -*devm_fpga_bridge_create(struct device *parent, const char *name,
> -			 const struct fpga_bridge_ops *br_ops, void *priv)
> +struct fpga_bridge *
> +fpga_bridge_register(struct device *parent, const char *name,
> +		     const struct fpga_bridge_ops *br_ops,
> +		     void *priv)
>   {
> -	struct fpga_bridge **ptr, *bridge;
> -
> -	ptr = devres_alloc(devm_fpga_bridge_release, sizeof(*ptr), GFP_KERNEL);
> -	if (!ptr)
> -		return NULL;
> -
> -	bridge = fpga_bridge_create(parent, name, br_ops, priv);
> -	if (!bridge) {
> -		devres_free(ptr);
> -	} else {
> -		*ptr = bridge;
> -		devres_add(parent, ptr);
> -	}
> +	struct fpga_bridge_info info = { 0 };
>   
> -	return bridge;
> -}
> -EXPORT_SYMBOL_GPL(devm_fpga_bridge_create);
> +	info.name = name;
> +	info.br_ops = br_ops;
> +	info.priv = priv;
>   
> -/**
> - * fpga_bridge_register - register an FPGA bridge
> - *
> - * @bridge: FPGA bridge struct
> - *
> - * Return: 0 for success, error code otherwise.
> - */
> -int fpga_bridge_register(struct fpga_bridge *bridge)
> -{
> -	struct device *dev = &bridge->dev;
> -	int ret;
> -
> -	ret = device_add(dev);
> -	if (ret)
> -		return ret;
> -
> -	of_platform_populate(dev->of_node, NULL, NULL, dev);
> -
> -	dev_info(dev->parent, "fpga bridge [%s] registered\n", bridge->name);
> -
> -	return 0;
> +	return fpga_bridge_register_full(parent, &info);
>   }
>   EXPORT_SYMBOL_GPL(fpga_bridge_register);
>   
> @@ -475,6 +430,10 @@ EXPORT_SYMBOL_GPL(fpga_bridge_unregister);
>   
>   static void fpga_bridge_dev_release(struct device *dev)
>   {
> +	struct fpga_bridge *bridge = to_fpga_bridge(dev);
> +
> +	ida_simple_remove(&fpga_bridge_ida, bridge->dev.id);
> +	kfree(bridge);
>   }
>   
>   static int __init fpga_bridge_dev_init(void)
> diff --git a/drivers/fpga/xilinx-pr-decoupler.c b/drivers/fpga/xilinx-pr-decoupler.c
> index ea2bde6e5bc4..c004e52b9464 100644
> --- a/drivers/fpga/xilinx-pr-decoupler.c
> +++ b/drivers/fpga/xilinx-pr-decoupler.c
> @@ -138,22 +138,17 @@ static int xlnx_pr_decoupler_probe(struct platform_device *pdev)
>   
>   	clk_disable(priv->clk);
>   
> -	br = devm_fpga_bridge_create(&pdev->dev, priv->ipconfig->name,
> -				     &xlnx_pr_decoupler_br_ops, priv);
> -	if (!br) {
> -		err = -ENOMEM;
> -		goto err_clk;
> -	}
> -
> -	platform_set_drvdata(pdev, br);
> -
> -	err = fpga_bridge_register(br);
> -	if (err) {
> +	br = fpga_bridge_register(&pdev->dev, priv->ipconfig->name,
> +				  &xlnx_pr_decoupler_br_ops, priv);
> +	if (IS_ERR(br)) {
> +		err = PTR_ERR(br);
>   		dev_err(&pdev->dev, "unable to register %s",
>   			priv->ipconfig->name);
>   		goto err_clk;
>   	}
>   
> +	platform_set_drvdata(pdev, br);
> +
>   	return 0;
>   
>   err_clk:
> diff --git a/include/linux/fpga/fpga-bridge.h b/include/linux/fpga/fpga-bridge.h
> index 6c3c28806ff1..f0a4d99d9c8e 100644
> --- a/include/linux/fpga/fpga-bridge.h
> +++ b/include/linux/fpga/fpga-bridge.h
> @@ -22,6 +22,23 @@ struct fpga_bridge_ops {
>   	const struct attribute_group **groups;

This groups seems to be unused.

If it is, maybe it should go into info.

Tom

>   };
>   
> +/**
> + * struct fpga_bridge_info - collection of parameters an FPGA Bridge
> + * @name: fpga bridge name
> + * @br_ops: pointer to structure of fpga bridge ops
> + * @priv: fpga bridge private data
> + *
> + * fpga_bridge_info contains parameters for the register 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_bridge_info {
> +	const char *name;
> +	const struct fpga_bridge_ops *br_ops;
> +	void *priv;
> +};
> +
>   /**
>    * struct fpga_bridge - FPGA bridge structure
>    * @name: name of low level FPGA bridge
> @@ -62,15 +79,13 @@ int of_fpga_bridge_get_to_list(struct device_node *np,
>   			       struct fpga_image_info *info,
>   			       struct list_head *bridge_list);
>   
> -struct fpga_bridge *fpga_bridge_create(struct device *dev, const char *name,
> -				       const struct fpga_bridge_ops *br_ops,
> -				       void *priv);
> -void fpga_bridge_free(struct fpga_bridge *br);
> -int fpga_bridge_register(struct fpga_bridge *br);
> -void fpga_bridge_unregister(struct fpga_bridge *br);
> +struct fpga_bridge *
> +fpga_bridge_register_full(struct device *parent, const struct fpga_bridge_info *info);
>   
> -struct fpga_bridge
> -*devm_fpga_bridge_create(struct device *dev, const char *name,
> -			 const struct fpga_bridge_ops *br_ops, void *priv);
> +struct fpga_bridge *
> +fpga_bridge_register(struct device *parent, const char *name,
> +		     const struct fpga_bridge_ops *br_ops,
> +		     void *priv);
> +void fpga_bridge_unregister(struct fpga_bridge *br);
>   
>   #endif /* _LINUX_FPGA_BRIDGE_H */