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 | 53 ++++++++++++++++++++++++++++++++++++++++------
 include/uapi/linux/rpmsg.h | 11 +++++++++-
 2 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index a271fce..97f80f4 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>
 #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 +317,35 @@ 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;
+	u32 val;
+	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);
+		break;
+	case RPMSG_SET_INCOMING_FLOWCONTROL:
+		ret = get_user(val, (int __user *)arg);
+		if (ret)
+			break;
+		set = !!arg;
+		ret = rpmsg_set_flow_control(eptdev->ept, set);
+		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
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Hi Sarannya,

kernel test robot noticed the following build errors:

[auto build test ERROR on v6.3-rc7]
[also build test ERROR on linus/master next-20230418]
[cannot apply to remoteproc/rpmsg-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Sarannya-S/rpmsg-core-Add-signal-API-support/20230419-220040
patch link:    https://lore.kernel.org/r/1681912409-25248-4-git-send-email-quic_sarannya%40quicinc.com
patch subject: [PATCH V6 3/3] rpmsg: char: Add RPMSG GET/SET FLOWCONTROL IOCTL support
config: m68k-allyesconfig (https://download.01.org/0day-ci/archive/20230420/202304200018.ik0k7dKN-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/4f765ede8c129f07c522ef4a7c6aee27cb466be6
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Sarannya-S/rpmsg-core-Add-signal-API-support/20230419-220040
        git checkout 4f765ede8c129f07c522ef4a7c6aee27cb466be6
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash drivers/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304200018.ik0k7dKN-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

   drivers/rpmsg/rpmsg_char.c: In function 'rpmsg_eptdev_ioctl':
>> drivers/rpmsg/rpmsg_char.c:334:23: error: too few arguments to function 'rpmsg_set_flow_control'
     334 |                 ret = rpmsg_set_flow_control(eptdev->ept, set);
         |                       ^~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/rpmsg/rpmsg_char.c:23:
   include/linux/rpmsg.h:200:5: note: declared here
     200 | int rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool enable, u32 dst);
         |     ^~~~~~~~~~~~~~~~~~~~~~
>> drivers/rpmsg/rpmsg_char.c:321:13: warning: variable 'val' set but not used [-Wunused-but-set-variable]
     321 |         u32 val;
         |             ^~~


vim +/rpmsg_set_flow_control +334 drivers/rpmsg/rpmsg_char.c

   314	
   315	static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
   316				       unsigned long arg)
   317	{
   318		struct rpmsg_eptdev *eptdev = fp->private_data;
   319	
   320		bool set;
 > 321		u32 val;
   322		int ret;
   323	
   324		switch (cmd) {
   325		case RPMSG_GET_OUTGOING_FLOWCONTROL:
   326			eptdev->remote_flow_updated = false;
   327			ret = put_user(eptdev->remote_flow, (int __user *)arg);
   328			break;
   329		case RPMSG_SET_INCOMING_FLOWCONTROL:
   330			ret = get_user(val, (int __user *)arg);
   331			if (ret)
   332				break;
   333			set = !!arg;
 > 334			ret = rpmsg_set_flow_control(eptdev->ept, set);
   335			break;
   336		case RPMSG_DESTROY_EPT_IOCTL:
   337			/* Don't allow to destroy a default endpoint. */
   338			if (eptdev->default_ept) {
   339				ret = -EINVAL;
   340				break;
   341			}
   342			ret = rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
   343			break;
   344		default:
   345			ret = -EINVAL;
   346		}
   347	
   348		return ret;
   349	}
   350	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests