Re: [PATCH V7 3/3] rpmsg: char: Add RPMSG GET/SET FLOWCONTROL IOCTL support

[Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>]

On 4/22/23 12:42, Sarannya S wrote:
> From: Chris Lew <quic_clew@quicinc.com>
> 
> Add RPMSG_GET_OUTGOING_FLOWCONTROL and RPMSG_SET_INCOMING_FLOWCONTROL
> IOCTL support for rpmsg char device nodes to get/set the low level
> transport signals.
> 
> Signed-off-by: Chris Lew <quic_clew@quicinc.com>
> Signed-off-by: Deepak Kumar Singh <quic_deesin@quicinc.com>
> Signed-off-by: Sarannya S <quic_sarannya@quicinc.com>
> ---
>  drivers/rpmsg/rpmsg_char.c | 49 ++++++++++++++++++++++++++++++++++++++++------
>  include/uapi/linux/rpmsg.h | 11 ++++++++++-
>  2 files changed, 53 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index a271fce..d50908f 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -23,6 +23,7 @@
>  #include <linux/rpmsg.h>
>  #include <linux/skbuff.h>
>  #include <linux/slab.h>
> +#include <linux/termios.h>

Seems useless now

>  #include <linux/uaccess.h>
>  #include <uapi/linux/rpmsg.h>
>  
> @@ -68,6 +69,8 @@ struct rpmsg_eptdev {
>  	struct sk_buff_head queue;
>  	wait_queue_head_t readq;
>  
> +	bool remote_flow;
> +	bool remote_flow_updated;
>  };
>  
>  int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
> @@ -116,6 +119,18 @@ static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void *buf, int len,
>  	return 0;
>  }
>  
> +static int rpmsg_ept_flow_cb(struct rpmsg_device *rpdev, void *priv, bool enable)
> +{
> +	struct rpmsg_eptdev *eptdev = priv;
> +
> +	eptdev->remote_flow = enable;
> +	eptdev->remote_flow_updated = true;
> +
> +	wake_up_interruptible(&eptdev->readq);
> +
> +	return 0;
> +}
> +
>  static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
>  {
>  	struct rpmsg_eptdev *eptdev = cdev_to_eptdev(inode->i_cdev);
> @@ -152,6 +167,7 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
>  		return -EINVAL;
>  	}
>  
> +	ept->flow_cb = rpmsg_ept_flow_cb;
>  	eptdev->ept = ept;
>  	filp->private_data = eptdev;
>  	mutex_unlock(&eptdev->ept_lock);
> @@ -172,6 +188,7 @@ static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
>  		eptdev->ept = NULL;
>  	}
>  	mutex_unlock(&eptdev->ept_lock);
> +	eptdev->remote_flow_updated = false;
>  
>  	/* Discard all SKBs */
>  	skb_queue_purge(&eptdev->queue);
> @@ -285,6 +302,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
>  	if (!skb_queue_empty(&eptdev->queue))
>  		mask |= EPOLLIN | EPOLLRDNORM;
>  
> +	if (eptdev->remote_flow_updated)
> +		mask |= EPOLLPRI;
> +
>  	mutex_lock(&eptdev->ept_lock);
>  	mask |= rpmsg_poll(eptdev->ept, filp, wait);
>  	mutex_unlock(&eptdev->ept_lock);
> @@ -297,14 +317,31 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
>  {
>  	struct rpmsg_eptdev *eptdev = fp->private_data;
>  
> -	if (cmd != RPMSG_DESTROY_EPT_IOCTL)
> -		return -EINVAL;
> +	bool set;
> +	int ret;
>  
> -	/* Don't allow to destroy a default endpoint. */
> -	if (eptdev->default_ept)
> -		return -EINVAL;
> +	switch (cmd) {
> +	case RPMSG_GET_OUTGOING_FLOWCONTROL:
> +		eptdev->remote_flow_updated = false;
> +		ret = put_user(eptdev->remote_flow, (int __user *)arg);

If the rpmsg_set_flow_control is not implemented on remote side or in the
backend then we should return true by default.
Else the communication should not be possible if eptdev->remote_flow is not
initialized.

Perhaps adding a "flow_ctrl" boolean in the rpmsg_device (similar to the
"announce") would give the information if the flow control is supported or not.
This "flow_ctrl" boolean would be initialized by the backend.

Regards
Arnaud


> +		break;
> +	case RPMSG_SET_INCOMING_FLOWCONTROL:
> +		set = !!arg;
> +		ret = rpmsg_set_flow_control(eptdev->ept, set, eptdev->chinfo.dst);
> +		break;
> +	case RPMSG_DESTROY_EPT_IOCTL:
> +		/* Don't allow to destroy a default endpoint. */
> +		if (eptdev->default_ept) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		ret = rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
>  
> -	return rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
> +	return ret;
>  }
>  
>  static const struct file_operations rpmsg_eptdev_fops = {
> diff --git a/include/uapi/linux/rpmsg.h b/include/uapi/linux/rpmsg.h
> index 1637e68..c955e27 100644
> --- a/include/uapi/linux/rpmsg.h
> +++ b/include/uapi/linux/rpmsg.h
> @@ -10,7 +10,6 @@
>  #include <linux/types.h>
>  
>  #define RPMSG_ADDR_ANY		0xFFFFFFFF
> -
>  /**
>   * struct rpmsg_endpoint_info - endpoint info representation
>   * @name: name of service
> @@ -43,4 +42,14 @@ struct rpmsg_endpoint_info {
>   */
>  #define RPMSG_RELEASE_DEV_IOCTL	_IOW(0xb5, 0x4, struct rpmsg_endpoint_info)
>  
> +/**
> + * Set the flow control for the remote rpmsg char device.
> + */
> +#define RPMSG_GET_OUTGOING_FLOWCONTROL _IOW(0xb5, 0x5, struct rpmsg_endpoint_info)
> +
> +/**
> + * Set the flow control for the local rpmsg char device.
> + */
> +#define RPMSG_SET_INCOMING_FLOWCONTROL _IOW(0xb5, 0x6, struct rpmsg_endpoint_info)
> +
>  #endif