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Message-ID: <6985175f-719a-bd4d-e95e-021b70234c8a@foss.st.com>
Date:   Mon, 10 Jul 2023 14:44:46 +0200
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Subject: Re: [PATCH V9 3/3] rpmsg: char: Add RPMSG GET/SET FLOWCONTROL IOCTL
 support
Content-Language: en-US
To:     Sarannya S <quic_sarannya@quicinc.com>,
        <quic_bjorande@quicinc.com>, <swboyd@chromium.org>,
        <quic_clew@quicinc.com>, <mathieu.poirier@linaro.org>
CC:     <linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <linux-remoteproc@vger.kernel.org>,
        Deepak Kumar Singh <quic_deesin@quicinc.com>,
        Bjorn Andersson <andersson@kernel.org>
References: <1688679698-31274-1-git-send-email-quic_sarannya@quicinc.com>
 <1688679698-31274-4-git-send-email-quic_sarannya@quicinc.com>
From:   Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>
Organization: STMicroelectronics
In-Reply-To: <1688679698-31274-4-git-send-email-quic_sarannya@quicinc.com>
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On 7/6/23 23:41, 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 | 54 ++++++++++++++++++++++++++++++++++++++++------
>  include/uapi/linux/rpmsg.h | 10 +++++++++
>  2 files changed, 58 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index a271fce..09833ad 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -52,6 +52,8 @@ static DEFINE_IDA(rpmsg_minor_ida);
>   * @readq:	wait object for incoming queue
>   * @default_ept: set to channel default endpoint if the default endpoint should be re-used
>   *              on device open to prevent endpoint address update.
> + * remote_flow_restricted: to indicate if the remote has requested for flow to be limited
> + * remote_flow_updated: to indicate if the flow control has been requested
>   */
>  struct rpmsg_eptdev {
>  	struct device dev;
> @@ -68,6 +70,8 @@ struct rpmsg_eptdev {
>  	struct sk_buff_head queue;
>  	wait_queue_head_t readq;
>  
> +	bool remote_flow_restricted;
> +	bool remote_flow_updated;
>  };
>  
>  int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
> @@ -116,6 +120,18 @@ 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_restricted = 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 +168,7 @@ 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 +189,7 @@ 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 +303,9 @@ 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 +318,35 @@ 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_restricted, (int __user *)arg);
> +		break;
> +	case RPMSG_SET_INCOMING_FLOWCONTROL:
> +		if (arg > 1) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		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..f0c8da2 100644
> --- a/include/uapi/linux/rpmsg.h
> +++ b/include/uapi/linux/rpmsg.h
> @@ -43,4 +43,14 @@ struct rpmsg_endpoint_info {
>   */
>  #define RPMSG_RELEASE_DEV_IOCTL	_IOW(0xb5, 0x4, struct rpmsg_endpoint_info)
>  
> +/**
> + * Get the flow control state of the remote rpmsg char device.
> + */
> +#define RPMSG_GET_OUTGOING_FLOWCONTROL _IOR(0xb5, 0x5, int)
> +
> +/**
> + * Set the flow control state of the local rpmsg char device.
> + */
> +#define RPMSG_SET_INCOMING_FLOWCONTROL _IOR(0xb5, 0x6, int)
> +

Seems that it is not the use to document the parameters for IOCTL
but I wonder if documenting the use of the RPMSG_GET_OUTGOING_FLOWCONTROL
and RPMSG_SET_INCOMING_FLOWCONTROL parameter could help users to implement
the IOCTL...

For the series
Acked-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>

Thanks,
Arnaud

>  #endif