RPMsg character device

RPMsg char driver (<tt>rpmsg_char.c</tt>)

**RT_RPMSG_DRIVER_EXPORT(rpmsg_char_driver)** — matches **rt_rpmsg_device** with **id.name** **rpmsg-char** or **rpmsg-raw** (set by **virtio-rpmsg.c**).

Prerequisite: transport + **rt_rpmsg_device_register** — see RPMsg (VirtIO stack).

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Topology

Device	Name pattern	Ops
Control	**rpmsg_charN**	**control** only — create/destroy endpoints
Per endpoint	**rpmsg_<src>x<dst>**	**read / write / control**

**probe**: allocates **rpmsg_char_ctrl**, stores in **rdev->parent.user_data**, registers control **rt_device**.

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Create endpoint

On control device:

struct rt_rpmsg_endpoint_info info;
 
rt_strncpy(info.name, "my-channel", RT_RPMSG_NAME_SIZE);
info.src = local_addr;
info.dst = remote_addr;
 
rt_device_control(ctrl, RT_DEVICE_CTRL_RPMSG_CREATE_EPT, &info);

Flow:

1. Default name **rpmsg-raw** if **info.name** empty
2. **rt_rpmsg_create_endpoint(rdev, &info, rpmsg_char_rx_callback)**
3. Ring buffer pool: **RT_RPMSG_CHAR_MSG_MAX** × **RT_RPMSG_CHAR_MSG_SIZE_MAX** (Kconfig)
4. Register char device **rpmsg_uxu**

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Data path

Direction	Path
TX	**write** → **rt_rpmsg_send**
RX	VirtIO/backend → endpoint cb → **rt_ringbuffer_put** → **read**
Overwrite	**RT_DEVICE_CTRL_RPMSG_DATA_OVERWRITE** → **put_force** when full

RX matching uses **find_endpoint** with **dst = incoming src**, **src = ANY** — addresses must match how the endpoint was created.

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Destroy

**RT_DEVICE_CTRL_RPMSG_DESTROY_EPT**: deferred via **rt_work** until **ref_count == 1** and device closed.

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See also

• RPMsg
• components/drivers/rpmsg/rpmsg_char.c