Introduce new eptdev abstraction based on anon inode. The new API is
exactly same with legacy one except:

- It's anonymous and devnode/path free.
- Its fops->open() is empty.

Signed-off-by: Dawei Li <dawei.li@linux.dev>
---
 drivers/rpmsg/rpmsg_char.c | 44 ++++++++++++++++++++++++++++++++++++++
 drivers/rpmsg/rpmsg_char.h | 19 ++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 5b2a883d6236..b0ec05f88013 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -13,6 +13,7 @@
 
 #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
 
+#include <linux/anon_inodes.h>
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/fs.h>
@@ -517,6 +518,49 @@ int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent
 }
 EXPORT_SYMBOL(rpmsg_chrdev_eptdev_create);
 
+static const struct file_operations rpmsg_eptdev_anon_fops = {
+	.owner = THIS_MODULE,
+	.release = rpmsg_eptdev_release,
+	.read_iter = rpmsg_eptdev_read_iter,
+	.write_iter = rpmsg_eptdev_write_iter,
+	.poll = rpmsg_eptdev_poll,
+	.unlocked_ioctl = rpmsg_eptdev_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+};
+
+int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
+			struct rpmsg_channel_info chinfo, int *pfd)
+{
+	struct rpmsg_eptdev *eptdev;
+	int ret, fd;
+
+	eptdev = __rpmsg_chrdev_eptdev_alloc(rpdev, parent, false);
+	if (IS_ERR(eptdev))
+		return PTR_ERR(eptdev);
+
+	ret =  __rpmsg_chrdev_eptdev_add(eptdev, chinfo, false);
+	if (ret) {
+		dev_err(&eptdev->dev, "failed to add %s\n", eptdev->chinfo.name);
+		return ret;
+	}
+
+	fd = anon_inode_getfd("rpmsg-eptdev", &rpmsg_eptdev_anon_fops, eptdev, O_RDWR | O_CLOEXEC);
+	if (fd < 0) {
+		put_device(&eptdev->dev);
+		return fd;
+	}
+
+	mutex_lock(&eptdev->ept_lock);
+	ret = __rpmsg_eptdev_open(eptdev);
+	mutex_unlock(&eptdev->ept_lock);
+
+	if (!ret)
+		*pfd = fd;
+
+	return ret;
+}
+EXPORT_SYMBOL(rpmsg_eptdev_create);
+
 static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
 {
 	struct rpmsg_channel_info chinfo;
diff --git a/drivers/rpmsg/rpmsg_char.h b/drivers/rpmsg/rpmsg_char.h
index 117d9cbc52f0..eb8a3b24f9fb 100644
--- a/drivers/rpmsg/rpmsg_char.h
+++ b/drivers/rpmsg/rpmsg_char.h
@@ -19,6 +19,19 @@
 int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
 			       struct rpmsg_channel_info chinfo);
 
+/**
+ * rpmsg_eptdev_create() - register ep device and its associated fd based on an endpoint
+ * @rpdev:  prepared rpdev to be used for creating endpoints
+ * @parent: parent device
+ * @chinfo: associated endpoint channel information.
+ * @pfd: fd in represent of endpoint device
+ *
+ * This function create a new rpmsg endpoint device and its associated fd to instantiate a new
+ * endpoint based on chinfo information.
+ */
+int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
+			struct rpmsg_channel_info chinfo, int *pfd);
+
 /**
  * rpmsg_chrdev_eptdev_destroy() - destroy created char device endpoint.
  * @data: private data associated to the endpoint device
@@ -36,6 +49,12 @@ static inline int rpmsg_chrdev_eptdev_create(struct rpmsg_device *rpdev, struct
 	return -ENXIO;
 }
 
+static inline int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
+				      struct rpmsg_channel_info chinfo, int *pfd);
+{
+	return -ENXIO;
+}
+
 static inline int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
 {
 	return -ENXIO;
-- 
2.25.1

Hi Dawei,

kernel test robot noticed the following build errors:

[auto build test ERROR on 92a09c47464d040866cf2b4cd052bc60555185fb]

url:    https://github.com/intel-lab-lkp/linux/commits/Dawei-Li/rpmsg-char-Reuse-eptdev-logic-for-anon-device/20250507-223209
base:   92a09c47464d040866cf2b4cd052bc60555185fb
patch link:    https://lore.kernel.org/r/20250507141712.4276-3-dawei.li%40linux.dev
patch subject: [PATCH 2/3] rpmsg: char: Implement eptdev based on anon inode
config: x86_64-randconfig-r052-20250508 (https://download.01.org/0day-ci/archive/20250509/202505090243.edAOs4uG-lkp@intel.com/config)
compiler: clang version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250509/202505090243.edAOs4uG-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505090243.edAOs4uG-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/rpmsg/rpmsg_ctrl.c:28:
>> drivers/rpmsg/rpmsg_char.h:54:1: error: expected identifier or '('
      54 | {
         | ^
   1 error generated.


vim +54 drivers/rpmsg/rpmsg_char.h

    51	
    52	static inline int rpmsg_eptdev_create(struct rpmsg_device *rpdev, struct device *parent,
    53					      struct rpmsg_channel_info chinfo, int *pfd);
  > 54	{
    55		return -ENXIO;
    56	}
    57	

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