linux-kernel - Re: [PATCH v2 04/16] rpmsg: ctrl: implement the ioctl function to create device

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Date:   Thu, 21 Jan 2021 16:52:58 -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 v2 04/16] rpmsg: ctrl: implement the ioctl function to
 create device

On Tue, Dec 22, 2020 at 11:57:14AM +0100, Arnaud Pouliquen wrote:
> Implement the ioctl function that parses the list of
> rpmsg drivers registered to create an associated device.
> To be ISO user API, in a first step, the driver_override
> is only allowed for the RPMsg raw service, supported by the
> rpmsg_char driver.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
>  drivers/rpmsg/rpmsg_ctrl.c | 43 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
> index 065e2e304019..8381b5b2b794 100644
> --- a/drivers/rpmsg/rpmsg_ctrl.c
> +++ b/drivers/rpmsg/rpmsg_ctrl.c
> @@ -56,12 +56,51 @@ static int rpmsg_ctrl_dev_open(struct inode *inode, struct file *filp)
>  	return 0;
>  }
>  
> +static const char *rpmsg_ctrl_get_drv_name(u32 service)
> +{
> +	struct rpmsg_ctl_info *drv_info;
> +
> +	list_for_each_entry(drv_info, &rpmsg_drv_list, node) {
> +		if (drv_info->ctrl->service == service)
> +			return drv_info->ctrl->drv_name;
> +	}
> +

I'm unsure about the above... To me this looks like what the .match() function
of a bus would do.  And when I read Bjorn's comment he brought up the
auxiliary_bus.  I don't know about the auxiliary_bus but it is worth looking
into.  Registering with a bus would streamline a lot of the code in this
patchset.

I'm out of time for today - I will continue tomorrow.

Thanks,
Mathieu

> +	return NULL;
> +}
> +
>  static long rpmsg_ctrl_dev_ioctl(struct file *fp, unsigned int cmd,
>  				 unsigned long arg)
>  {
>  	struct rpmsg_ctrl_dev *ctrldev = fp->private_data;
> -
> -	dev_info(&ctrldev->dev, "Control not yet implemented\n");
> +	void __user *argp = (void __user *)arg;
> +	struct rpmsg_channel_info chinfo;
> +	struct rpmsg_endpoint_info eptinfo;
> +	struct rpmsg_device *newch;
> +
> +	if (cmd != RPMSG_CREATE_EPT_IOCTL)
> +		return -EINVAL;
> +
> +	if (copy_from_user(&eptinfo, argp, sizeof(eptinfo)))
> +		return -EFAULT;
> +
> +	/*
> +	 * In a frst step only the rpmsg_raw service is supported.
> +	 * The override is foorced to RPMSG_RAW_SERVICE
> +	 */
> +	chinfo.driver_override = rpmsg_ctrl_get_drv_name(RPMSG_RAW_SERVICE);
> +	if (!chinfo.driver_override)
> +		return -ENODEV;
> +
> +	memcpy(chinfo.name, eptinfo.name, RPMSG_NAME_SIZE);
> +	chinfo.name[RPMSG_NAME_SIZE - 1] = '\0';
> +	chinfo.src = eptinfo.src;
> +	chinfo.dst = eptinfo.dst;
> +
> +	newch = rpmsg_create_channel(ctrldev->rpdev, &chinfo);
> +	if (!newch) {
> +		dev_err(&ctrldev->dev, "rpmsg_create_channel failed\n");
> +		return -ENXIO;
> +	}
>  
>  	return 0;
>  };
> -- 
> 2.17.1
>