+============================================
Remote Processor Messaging (rpmsg) Framework
+============================================
-Note: this document describes the rpmsg bus and how to write rpmsg drivers.
-To learn how to add rpmsg support for new platforms, check out remoteproc.txt
-(also a resident of Documentation/).
+.. note::
-1. Introduction
+ This document describes the rpmsg bus and how to write rpmsg drivers.
+ To learn how to add rpmsg support for new platforms, check out remoteproc.txt
+ (also a resident of Documentation/).
+
+Introduction
+============
Modern SoCs typically employ heterogeneous remote processor devices in
asymmetric multiprocessing (AMP) configurations, which may be running
with the payload of the inbound message).
-2. User API
+User API
+========
+
+::
int rpmsg_send(struct rpmsg_channel *rpdev, void *data, int len);
- - sends a message across to the remote processor on a given channel.
- The caller should specify the channel, the data it wants to send,
- and its length (in bytes). The message will be sent on the specified
- channel, i.e. its source and destination address fields will be
- set to the channel's src and dst addresses.
-
- In case there are no TX buffers available, the function will block until
- one becomes available (i.e. until the remote processor consumes
- a tx buffer and puts it back on virtio's used descriptor ring),
- or a timeout of 15 seconds elapses. When the latter happens,
- -ERESTARTSYS is returned.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+
+sends a message across to the remote processor on a given channel.
+The caller should specify the channel, the data it wants to send,
+and its length (in bytes). The message will be sent on the specified
+channel, i.e. its source and destination address fields will be
+set to the channel's src and dst addresses.
+
+In case there are no TX buffers available, the function will block until
+one becomes available (i.e. until the remote processor consumes
+a tx buffer and puts it back on virtio's used descriptor ring),
+or a timeout of 15 seconds elapses. When the latter happens,
+-ERESTARTSYS is returned.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
int rpmsg_sendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst);
- - sends a message across to the remote processor on a given channel,
- to a destination address provided by the caller.
- The caller should specify the channel, the data it wants to send,
- its length (in bytes), and an explicit destination address.
- The message will then be sent to the remote processor to which the
- channel belongs, using the channel's src address, and the user-provided
- dst address (thus the channel's dst address will be ignored).
-
- In case there are no TX buffers available, the function will block until
- one becomes available (i.e. until the remote processor consumes
- a tx buffer and puts it back on virtio's used descriptor ring),
- or a timeout of 15 seconds elapses. When the latter happens,
- -ERESTARTSYS is returned.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+
+sends a message across to the remote processor on a given channel,
+to a destination address provided by the caller.
+
+The caller should specify the channel, the data it wants to send,
+its length (in bytes), and an explicit destination address.
+
+The message will then be sent to the remote processor to which the
+channel belongs, using the channel's src address, and the user-provided
+dst address (thus the channel's dst address will be ignored).
+
+In case there are no TX buffers available, the function will block until
+one becomes available (i.e. until the remote processor consumes
+a tx buffer and puts it back on virtio's used descriptor ring),
+or a timeout of 15 seconds elapses. When the latter happens,
+-ERESTARTSYS is returned.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
int rpmsg_send_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
void *data, int len);
- - sends a message across to the remote processor, using the src and dst
- addresses provided by the user.
- The caller should specify the channel, the data it wants to send,
- its length (in bytes), and explicit source and destination addresses.
- The message will then be sent to the remote processor to which the
- channel belongs, but the channel's src and dst addresses will be
- ignored (and the user-provided addresses will be used instead).
-
- In case there are no TX buffers available, the function will block until
- one becomes available (i.e. until the remote processor consumes
- a tx buffer and puts it back on virtio's used descriptor ring),
- or a timeout of 15 seconds elapses. When the latter happens,
- -ERESTARTSYS is returned.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+
+
+sends a message across to the remote processor, using the src and dst
+addresses provided by the user.
+
+The caller should specify the channel, the data it wants to send,
+its length (in bytes), and explicit source and destination addresses.
+The message will then be sent to the remote processor to which the
+channel belongs, but the channel's src and dst addresses will be
+ignored (and the user-provided addresses will be used instead).
+
+In case there are no TX buffers available, the function will block until
+one becomes available (i.e. until the remote processor consumes
+a tx buffer and puts it back on virtio's used descriptor ring),
+or a timeout of 15 seconds elapses. When the latter happens,
+-ERESTARTSYS is returned.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
int rpmsg_trysend(struct rpmsg_channel *rpdev, void *data, int len);
- - sends a message across to the remote processor on a given channel.
- The caller should specify the channel, the data it wants to send,
- and its length (in bytes). The message will be sent on the specified
- channel, i.e. its source and destination address fields will be
- set to the channel's src and dst addresses.
- In case there are no TX buffers available, the function will immediately
- return -ENOMEM without waiting until one becomes available.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+sends a message across to the remote processor on a given channel.
+The caller should specify the channel, the data it wants to send,
+and its length (in bytes). The message will be sent on the specified
+channel, i.e. its source and destination address fields will be
+set to the channel's src and dst addresses.
+
+In case there are no TX buffers available, the function will immediately
+return -ENOMEM without waiting until one becomes available.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
int rpmsg_trysendto(struct rpmsg_channel *rpdev, void *data, int len, u32 dst)
- - sends a message across to the remote processor on a given channel,
- to a destination address provided by the user.
- The user should specify the channel, the data it wants to send,
- its length (in bytes), and an explicit destination address.
- The message will then be sent to the remote processor to which the
- channel belongs, using the channel's src address, and the user-provided
- dst address (thus the channel's dst address will be ignored).
-
- In case there are no TX buffers available, the function will immediately
- return -ENOMEM without waiting until one becomes available.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+
+
+sends a message across to the remote processor on a given channel,
+to a destination address provided by the user.
+
+The user should specify the channel, the data it wants to send,
+its length (in bytes), and an explicit destination address.
+
+The message will then be sent to the remote processor to which the
+channel belongs, using the channel's src address, and the user-provided
+dst address (thus the channel's dst address will be ignored).
+
+In case there are no TX buffers available, the function will immediately
+return -ENOMEM without waiting until one becomes available.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
int rpmsg_trysend_offchannel(struct rpmsg_channel *rpdev, u32 src, u32 dst,
void *data, int len);
- - sends a message across to the remote processor, using source and
- destination addresses provided by the user.
- The user should specify the channel, the data it wants to send,
- its length (in bytes), and explicit source and destination addresses.
- The message will then be sent to the remote processor to which the
- channel belongs, but the channel's src and dst addresses will be
- ignored (and the user-provided addresses will be used instead).
-
- In case there are no TX buffers available, the function will immediately
- return -ENOMEM without waiting until one becomes available.
- The function can only be called from a process context (for now).
- Returns 0 on success and an appropriate error value on failure.
+
+
+sends a message across to the remote processor, using source and
+destination addresses provided by the user.
+
+The user should specify the channel, the data it wants to send,
+its length (in bytes), and explicit source and destination addresses.
+The message will then be sent to the remote processor to which the
+channel belongs, but the channel's src and dst addresses will be
+ignored (and the user-provided addresses will be used instead).
+
+In case there are no TX buffers available, the function will immediately
+return -ENOMEM without waiting until one becomes available.
+
+The function can only be called from a process context (for now).
+Returns 0 on success and an appropriate error value on failure.
+
+::
struct rpmsg_endpoint *rpmsg_create_ept(struct rpmsg_channel *rpdev,
void (*cb)(struct rpmsg_channel *, void *, int, void *, u32),
void *priv, u32 addr);
- - every rpmsg address in the system is bound to an rx callback (so when
- inbound messages arrive, they are dispatched by the rpmsg bus using the
- appropriate callback handler) by means of an rpmsg_endpoint struct.
-
- This function allows drivers to create such an endpoint, and by that,
- bind a callback, and possibly some private data too, to an rpmsg address
- (either one that is known in advance, or one that will be dynamically
- assigned for them).
-
- Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
- is already created for them when they are probed by the rpmsg bus
- (using the rx callback they provide when they registered to the rpmsg bus).
-
- So things should just work for simple drivers: they already have an
- endpoint, their rx callback is bound to their rpmsg address, and when
- relevant inbound messages arrive (i.e. messages which their dst address
- equals to the src address of their rpmsg channel), the driver's handler
- is invoked to process it.
-
- That said, more complicated drivers might do need to allocate
- additional rpmsg addresses, and bind them to different rx callbacks.
- To accomplish that, those drivers need to call this function.
- Drivers should provide their channel (so the new endpoint would bind
- to the same remote processor their channel belongs to), an rx callback
- function, an optional private data (which is provided back when the
- rx callback is invoked), and an address they want to bind with the
- callback. If addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
- dynamically assign them an available rpmsg address (drivers should have
- a very good reason why not to always use RPMSG_ADDR_ANY here).
-
- Returns a pointer to the endpoint on success, or NULL on error.
+
+every rpmsg address in the system is bound to an rx callback (so when
+inbound messages arrive, they are dispatched by the rpmsg bus using the
+appropriate callback handler) by means of an rpmsg_endpoint struct.
+
+This function allows drivers to create such an endpoint, and by that,
+bind a callback, and possibly some private data too, to an rpmsg address
+(either one that is known in advance, or one that will be dynamically
+assigned for them).
+
+Simple rpmsg drivers need not call rpmsg_create_ept, because an endpoint
+is already created for them when they are probed by the rpmsg bus
+(using the rx callback they provide when they registered to the rpmsg bus).
+
+So things should just work for simple drivers: they already have an
+endpoint, their rx callback is bound to their rpmsg address, and when
+relevant inbound messages arrive (i.e. messages which their dst address
+equals to the src address of their rpmsg channel), the driver's handler
+is invoked to process it.
+
+That said, more complicated drivers might do need to allocate
+additional rpmsg addresses, and bind them to different rx callbacks.
+To accomplish that, those drivers need to call this function.
+Drivers should provide their channel (so the new endpoint would bind
+to the same remote processor their channel belongs to), an rx callback
+function, an optional private data (which is provided back when the
+rx callback is invoked), and an address they want to bind with the
+callback. If addr is RPMSG_ADDR_ANY, then rpmsg_create_ept will
+dynamically assign them an available rpmsg address (drivers should have
+a very good reason why not to always use RPMSG_ADDR_ANY here).
+
+Returns a pointer to the endpoint on success, or NULL on error.
+
+::
void rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
- - destroys an existing rpmsg endpoint. user should provide a pointer
- to an rpmsg endpoint that was previously created with rpmsg_create_ept().
+
+
+destroys an existing rpmsg endpoint. user should provide a pointer
+to an rpmsg endpoint that was previously created with rpmsg_create_ept().
+
+::
int register_rpmsg_driver(struct rpmsg_driver *rpdrv);
- - registers an rpmsg driver with the rpmsg bus. user should provide
- a pointer to an rpmsg_driver struct, which contains the driver's
- ->probe() and ->remove() functions, an rx callback, and an id_table
- specifying the names of the channels this driver is interested to
- be probed with.
+
+
+registers an rpmsg driver with the rpmsg bus. user should provide
+a pointer to an rpmsg_driver struct, which contains the driver's
+->probe() and ->remove() functions, an rx callback, and an id_table
+specifying the names of the channels this driver is interested to
+be probed with.
+
+::
void unregister_rpmsg_driver(struct rpmsg_driver *rpdrv);
- - unregisters an rpmsg driver from the rpmsg bus. user should provide
- a pointer to a previously-registered rpmsg_driver struct.
- Returns 0 on success, and an appropriate error value on failure.
-3. Typical usage
+unregisters an rpmsg driver from the rpmsg bus. user should provide
+a pointer to a previously-registered rpmsg_driver struct.
+Returns 0 on success, and an appropriate error value on failure.
+
+
+Typical usage
+=============
The following is a simple rpmsg driver, that sends an "hello!" message
on probe(), and whenever it receives an incoming message, it dumps its
content to the console.
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/rpmsg.h>
+::
+
+ #include <linux/kernel.h>
+ #include <linux/module.h>
+ #include <linux/rpmsg.h>
-static void rpmsg_sample_cb(struct rpmsg_channel *rpdev, void *data, int len,
+ static void rpmsg_sample_cb(struct rpmsg_channel *rpdev, void *data, int len,
void *priv, u32 src)
-{
+ {
print_hex_dump(KERN_INFO, "incoming message:", DUMP_PREFIX_NONE,
16, 1, data, len, true);
-}
+ }
-static int rpmsg_sample_probe(struct rpmsg_channel *rpdev)
-{
+ static int rpmsg_sample_probe(struct rpmsg_channel *rpdev)
+ {
int err;
dev_info(&rpdev->dev, "chnl: 0x%x -> 0x%x\n", rpdev->src, rpdev->dst);
}
return 0;
-}
+ }
-static void rpmsg_sample_remove(struct rpmsg_channel *rpdev)
-{
+ static void rpmsg_sample_remove(struct rpmsg_channel *rpdev)
+ {
dev_info(&rpdev->dev, "rpmsg sample client driver is removed\n");
-}
+ }
-static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = {
+ static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = {
{ .name = "rpmsg-client-sample" },
{ },
-};
-MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_sample_id_table);
+ };
+ MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_sample_id_table);
-static struct rpmsg_driver rpmsg_sample_client = {
+ static struct rpmsg_driver rpmsg_sample_client = {
.drv.name = KBUILD_MODNAME,
.id_table = rpmsg_driver_sample_id_table,
.probe = rpmsg_sample_probe,
.callback = rpmsg_sample_cb,
.remove = rpmsg_sample_remove,
-};
-module_rpmsg_driver(rpmsg_sample_client);
+ };
+ module_rpmsg_driver(rpmsg_sample_client);
+
+.. note::
-Note: a similar sample which can be built and loaded can be found
-in samples/rpmsg/.
+ a similar sample which can be built and loaded can be found
+ in samples/rpmsg/.
-4. Allocations of rpmsg channels:
+Allocations of rpmsg channels
+=============================
At this point we only support dynamic allocations of rpmsg channels.
projects / mirror_ubuntu-eoan-kernel.git / commitdiff