linux-kernel - Re: [PATCH v7 1/5] driver core: Introduce device_{add,remove}_of

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Message-ID: <20250219155901.000009e4@huawei.com>
Date: Wed, 19 Feb 2025 15:59:01 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Herve Codina <herve.codina@...tlin.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>, Rob Herring
	<robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, Bjorn Helgaas
	<bhelgaas@...gle.com>, Lizhi Hou <lizhi.hou@....com>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, Allan Nielsen <allan.nielsen@...rochip.com>,
	Horatiu Vultur <horatiu.vultur@...rochip.com>, Steen Hegelund
	<steen.hegelund@...rochip.com>, Thomas Petazzoni
	<thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v7 1/5] driver core: Introduce
 device_{add,remove}_of_node()

On Tue,  4 Feb 2025 08:34:56 +0100
Herve Codina <herve.codina@...tlin.com> wrote:

> An of_node can be set to a device using device_set_node().
> This function cannot prevent any of_node and/or fwnode overwrites.
> 
> When adding an of_node on an already present device, the following
> operations need to be done:
> - Attach the of_node if no of_node were already attached
> - Attach the of_node as a fwnode if no fwnode were already attached
> 
> This is the purpose of device_add_of_node().
> device_remove_of_node() reverts the operations done by
> device_add_of_node().
> 
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
A few passing comments. Not suggestions to actually change anything
at this stage though. Maybe a potential follow up if you think it's
a good idea.

> ---
>  drivers/base/core.c    | 61 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/device.h |  2 ++
>  2 files changed, 63 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 5a1f05198114..d1b044af64de 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -5170,6 +5170,67 @@ void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode)
>  }
>  EXPORT_SYMBOL_GPL(set_secondary_fwnode);
>  
> +/**
> + * device_remove_of_node - Remove an of_node from a device
> + * @dev: device whose device-tree node is being removed
> + */
> +void device_remove_of_node(struct device *dev)
> +{
> +	dev = get_device(dev);
> +	if (!dev)
> +		return;
Maybe use
	struct device *d __free(put_device) = get_device(dev);

	if (!d->of_node);
		return;

Not a reason to respin though!


> +
> +	if (!dev->of_node)
> +		goto end;
> +
> +	if (dev->fwnode == of_fwnode_handle(dev->of_node))
> +		dev->fwnode = NULL;
> +
> +	of_node_put(dev->of_node);
> +	dev->of_node = NULL;
> +
> +end:
> +	put_device(dev);
> +}
> +EXPORT_SYMBOL_GPL(device_remove_of_node);
> +
> +/**
> + * device_add_of_node - Add an of_node to an existing device
> + * @dev: device whose device-tree node is being added
> + * @of_node: of_node to add
> + *
> + * Return: 0 on success or error code on failure.
> + */
> +int device_add_of_node(struct device *dev, struct device_node *of_node)
> +{
> +	int ret;
> +
> +	if (!of_node)
> +		return -EINVAL;
> +
> +	dev = get_device(dev);

Likewise could use __free() magic here as well for slight simpliciations.

> +	if (!dev)
> +		return -EINVAL;
> +
> +	if (dev->of_node) {
> +		dev_err(dev, "Cannot replace node %pOF with %pOF\n",
> +			dev->of_node, of_node);
> +		ret = -EBUSY;
> +		goto end;
> +	}
> +
> +	dev->of_node = of_node_get(of_node);
> +
> +	if (!dev->fwnode)
> +		dev->fwnode = of_fwnode_handle(of_node);
> +
> +	ret = 0;
> +end:
> +	put_device(dev);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(device_add_of_node);
> +
>  /**
>   * device_set_of_node_from_dev - reuse device-tree node of another device
>   * @dev: device whose device-tree node is being set
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 80a5b3268986..1244e5892292 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -1191,6 +1191,8 @@ int device_online(struct device *dev);
>  void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
>  void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
>  void device_set_node(struct device *dev, struct fwnode_handle *fwnode);
> +int device_add_of_node(struct device *dev, struct device_node *of_node);
> +void device_remove_of_node(struct device *dev);
>  void device_set_of_node_from_dev(struct device *dev, const struct device *dev2);
>  
>  static inline struct device_node *dev_of_node(struct device *dev)