linux-kernel - Re: [PATCH v5 16/16] rpmsg: char: return an error if device already open

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Date:   Thu, 4 Mar 2021 11:45:29 -0700
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 v5 16/16] rpmsg: char: return an error if device already
 open

On Fri, Feb 19, 2021 at 12:15:01PM +0100, Arnaud Pouliquen wrote:
> The rpmsg_create_ept function is invoked when the device is opened.
> As only one endpoint must be created per device. It is not possible to
> open the same device twice. But there is nothing to prevent multi open.

s/multi/multiple

> Return -EBUSY when device is already opened to have a generic error
> instead of relying on the back-end to potentially detect the error.
> 
> Without this patch for instance the GLINK driver return -EBUSY while
> the virtio bus return -ENOSPC.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
>  drivers/rpmsg/rpmsg_char.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 8d3f9d6c20ad..4cd5b79559f0 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -116,6 +116,9 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
>  	struct device *dev = &eptdev->dev;
>  	u32 addr = eptdev->chinfo.src;
>  
> +	if (eptdev->ept)
> +		return -EBUSY;
> +

It would be nice to return the same error code regardless of the backend but at
the same time I feel like it isn't the right place to do this.  I need to think
about this one but for now we can keep it.

>  	get_device(dev);
>  
>  	/*
> -- 
> 2.17.1
>