linux-kernel - Re: [PATCH 2/2] remoteproc: core: Register the character device interface

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Message-ID: <20200330221338.GB17782@xps15>
Date:   Mon, 30 Mar 2020 16:13:38 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        bjorn.andersson@...aro.org, ohad@...ery.com,
        psodagud@...eaurora.org, tsoni@...eaurora.org,
        sidgup@...eaurora.org
Subject: Re: [PATCH 2/2] remoteproc: core: Register the character device
 interface

On Thu, Mar 26, 2020 at 09:50:40AM -0700, Rishabh Bhatnagar wrote:
> Add the character device during rproc_add. This would create
> a character device node at /dev/subsys_<rproc_name>. Userspace
> applications can interact with the remote processor using this
> interface rather than using sysfs node. To distinguish between
> different remote processor nodes the device name has been changed
> to include the rproc name appended to "rproc_" string.
> 
> Change-Id: I2114f77f8d2b5fd97e281021ec9905ef5c2fb54c
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> ---
>  drivers/remoteproc/remoteproc_core.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 097f33e..f657983 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1907,6 +1907,12 @@ int rproc_add(struct rproc *rproc)
>  	struct device *dev = &rproc->dev;
>  	int ret;
>  
> +	ret = rproc_char_device_add(rproc);
> +	if (ret) {
> +		pr_err("error while adding character device\n");
> +		return ret;
> +	}
> +
>  	ret = device_add(dev);
>  	if (ret < 0)
>  		return ret;
> @@ -2044,7 +2050,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
>  		return NULL;
>  	}
>  
> -	dev_set_name(&rproc->dev, "remoteproc%d", rproc->index);
> +	dev_set_name(&rproc->dev, "rproc_%s", rproc->name);

Unfortunately you can't do that. The name of the remoteproc in sysfs is visible
by users and a lot of scripts will fail because of this change.

>  
>  	atomic_set(&rproc->power, 0);
>  
> @@ -2220,6 +2226,7 @@ static int __init remoteproc_init(void)
>  {
>  	rproc_init_sysfs();
>  	rproc_init_debugfs();
> +	rproc_init_cdev();
>  
>  	return 0;
>  }
> @@ -2231,6 +2238,7 @@ static void __exit remoteproc_exit(void)
>  
>  	rproc_exit_debugfs();
>  	rproc_exit_sysfs();
> +	rproc_exit_cdev();
>  }
>  module_exit(remoteproc_exit);
>  
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project