linux-kernel - Re: [PATCH 5/7] rpmsg: char: Introduce a rpmsg driver for the rpmsg char device

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Message-ID: <20210412195331.GA582352@xps15>
Date:   Mon, 12 Apr 2021 13:53:31 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Andy Gross <agross@...nel.org>,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 5/7] rpmsg: char: Introduce a rpmsg driver for the rpmsg
 char device

On Tue, Mar 23, 2021 at 01:27:35PM +0100, Arnaud Pouliquen wrote:
> A rpmsg char device allows to probe the endpoint device on a remote name
> service announcement.
> 
> With this patch the /dev/rpmsgX interface is created either by a user
> application or by the remote firmware.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
>  drivers/rpmsg/rpmsg_char.c | 58 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 57 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 7f6d46078179..69e774edb74b 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -28,6 +28,8 @@
>  
>  #define RPMSG_DEV_MAX	(MINORMASK + 1)
>  
> +#define RPMSG_CHAR_DEVNAME "rpmsg-raw"
> +
>  static dev_t rpmsg_major;
>  
>  static DEFINE_IDA(rpmsg_ept_ida);
> @@ -405,13 +407,67 @@ int rpmsg_chrdev_create_eptdev(struct rpmsg_device *rpdev, struct device *parent
>  }
>  EXPORT_SYMBOL(rpmsg_chrdev_create_eptdev);
>  
> +static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
> +{
> +	struct rpmsg_channel_info chinfo;
> +	struct rpmsg_eptdev *eptdev;
> +
> +	if (!rpdev->ept)
> +		return -EINVAL;
> +
> +	memcpy(chinfo.name, RPMSG_CHAR_DEVNAME, sizeof(RPMSG_CHAR_DEVNAME));
> +	chinfo.src = rpdev->src;
> +	chinfo.dst = rpdev->dst;
> +
> +	eptdev = __rpmsg_chrdev_create_eptdev(rpdev, &rpdev->dev, chinfo, NULL);
> +	if (IS_ERR(eptdev))
> +		return PTR_ERR(eptdev);
> +
> +	/* Set the private field of the default endpoint to retrieve context on callback. */
> +	rpdev->ept->priv = eptdev;
> +
> +	return 0;
> +}
> +
> +static void rpmsg_chrdev_remove(struct rpmsg_device *rpdev)
> +{
> +	int ret;
> +
> +	ret = device_for_each_child(&rpdev->dev, NULL, rpmsg_chrdev_destroy_eptdev);
> +	if (ret)
> +		dev_warn(&rpdev->dev, "failed to destroy endpoints: %d\n", ret);
> +}
> +
> +static struct rpmsg_device_id rpmsg_chrdev_id_table[] = {
> +	{ .name	= RPMSG_CHAR_DEVNAME },
> +	{ },
> +};
> +
> +static struct rpmsg_driver rpmsg_chrdev_driver = {
> +	.probe = rpmsg_chrdev_probe,
> +	.remove = rpmsg_chrdev_remove,
> +	.id_table = rpmsg_chrdev_id_table,
> +	.callback = rpmsg_ept_cb,
> +	.drv = {
> +		.name = "rpmsg_chrdev",
> +	},
> +};
> +
>  static int rpmsg_chrdev_init(void)
>  {
>  	int ret;
>  
>  	ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg");
> -	if (ret < 0)
> +	if (ret < 0) {
>  		pr_err("rpmsg: failed to allocate char dev region\n");
> +		return ret;
> +	}
> +
> +	ret = register_rpmsg_driver(&rpmsg_chrdev_driver);
> +	if (ret < 0) {
> +		pr_err("rpmsg: failed to register rpmsg raw driver\n");
> +		unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
> +	}

Function unregister_rpmsg_driver() has to be called in rpmsg_chrdev_exit().

>  
>  	return ret;
>  }
> -- 
> 2.17.1
>