linux-kernel - Re: [PATCH v2 2/3] rpmsg: char: Implement eptdev based on anon inode

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Message-ID: <aCZNqVbGKa_EaCBT@p14s>
Date: Thu, 15 May 2025 14:25:13 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Dawei Li <dawei.li@...ux.dev>
Cc: andersson@...nel.org, linux-remoteproc@...r.kernel.org,
	linux-kernel@...r.kernel.org, set_pte_at@...look.com
Subject: Re: [PATCH v2 2/3] rpmsg: char: Implement eptdev based on anon inode

On Fri, May 09, 2025 at 11:59:26PM +0800, Dawei Li wrote:
> Introduce new eptdev abstraction based on anon inode. The new API is
> exactly same with legacy one except:
> 
> - It's anonymous and devnode/path free.
> - Its fops->open() is empty.
> 
> Signed-off-by: Dawei Li <dawei.li@...ux.dev>
> ---
>  drivers/rpmsg/rpmsg_char.c | 44 ++++++++++++++++++++++++++++++++++++++
>  drivers/rpmsg/rpmsg_char.h | 19 ++++++++++++++++
>  2 files changed, 63 insertions(+)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 5b2a883d6236..b0ec05f88013 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -13,6 +13,7 @@
>  
>  #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
>  
> +#include <linux/anon_inodes.h>
>  #include <linux/cdev.h>
>  #include <linux/device.h>
>  #include <linux/fs.h>
> @@ -517,6 +518,49 @@ int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent
>  }
>  EXPORT_SYMBOL(rpmsg_chrdev_eptdev_create);
>  
> +static const struct file_operations rpmsg_eptdev_anon_fops = {
> +	.owner = THIS_MODULE,
> +	.release = rpmsg_eptdev_release,
> +	.read_iter = rpmsg_eptdev_read_iter,
> +	.write_iter = rpmsg_eptdev_write_iter,
> +	.poll = rpmsg_eptdev_poll,
> +	.unlocked_ioctl = rpmsg_eptdev_ioctl,
> +	.compat_ioctl = compat_ptr_ioctl,
> +};
> +
> +int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
> +			struct rpmsg_channel_info chinfo, int *pfd)

rpmsg_anonymous_eptdev_create()

> +{
> +	struct rpmsg_eptdev *eptdev;
> +	int ret, fd;
> +
> +	eptdev = __rpmsg_chrdev_eptdev_alloc(rpdev, parent, false);
> +	if (IS_ERR(eptdev))
> +		return PTR_ERR(eptdev);
> +
> +	ret =  __rpmsg_chrdev_eptdev_add(eptdev, chinfo, false);
> +	if (ret) {
> +		dev_err(&eptdev->dev, "failed to add %s\n", eptdev->chinfo.name);
> +		return ret;
> +	}
> +
> +	fd = anon_inode_getfd("rpmsg-eptdev", &rpmsg_eptdev_anon_fops, eptdev, O_RDWR | O_CLOEXEC);
> +	if (fd < 0) {
> +		put_device(&eptdev->dev);
> +		return fd;
> +	}
> +
> +	mutex_lock(&eptdev->ept_lock);
> +	ret = __rpmsg_eptdev_open(eptdev);
> +	mutex_unlock(&eptdev->ept_lock);
> +
> +	if (!ret)
> +		*pfd = fd;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(rpmsg_eptdev_create);
> +
>  static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
>  {
>  	struct rpmsg_channel_info chinfo;
> diff --git a/drivers/rpmsg/rpmsg_char.h b/drivers/rpmsg/rpmsg_char.h
> index 117d9cbc52f0..8cc2c14537da 100644
> --- a/drivers/rpmsg/rpmsg_char.h
> +++ b/drivers/rpmsg/rpmsg_char.h
> @@ -19,6 +19,19 @@
>  int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
>  			       struct rpmsg_channel_info chinfo);
>  
> +/**
> + * rpmsg_eptdev_create() - register ep device and its associated fd based on an endpoint
> + * @rpdev:  prepared rpdev to be used for creating endpoints
> + * @parent: parent device
> + * @chinfo: associated endpoint channel information.
> + * @pfd: fd in represent of endpoint device
> + *
> + * This function create a new rpmsg endpoint device and its associated fd to instantiate a new
> + * endpoint based on chinfo information.
> + */
> +int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
> +			struct rpmsg_channel_info chinfo, int *pfd);
> +
>  /**
>   * rpmsg_chrdev_eptdev_destroy() - destroy created char device endpoint.
>   * @data: private data associated to the endpoint device
> @@ -36,6 +49,12 @@ static inline int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct
>  	return -ENXIO;
>  }
>  
> +static inline int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
> +				      struct rpmsg_channel_info chinfo, int *pfd)
> +{
> +	return -ENXIO;
> +}
> +
>  static inline int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
>  {
>  	return -ENXIO;
> -- 
> 2.25.1
>