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

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Date:   Tue, 24 Mar 2020 21:22:57 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Rishabh Bhatnagar <rishabhb@...eaurora.org>
Cc:     linux-remoteproc-owner@...r.kernel.org,
        linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
        psodagud@...eaurora.org, tsoni@...eaurora.org,
        sidgup@...eaurora.org
Subject: Re: [PATCH 2/2] remoteproc: core: Register the character device
 interface

On Fri 20 Mar 16:36 PDT 2020, 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 "subsys_" string.
> 
> Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
> ---
>  drivers/remoteproc/remoteproc_core.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 097f33e..48a3932 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, "subsys_%s", rproc->name);

Afaict there's no guarantee that rproc->name is unique and I wonder if
this will break any userspace expectations. Please repost this to
remoteproc@ so we can get further input on this.

And if we can do this, I would like it to be "rproc-%s".

Regards,
Bjorn

>  
>  	atomic_set(&rproc->power, 0);
>  
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project