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Diffstat (limited to 'Documentation/rpmsg.txt')
| -rw-r--r-- | Documentation/rpmsg.txt | 348 |
1 files changed, 204 insertions, 144 deletions
diff --git a/Documentation/rpmsg.txt b/Documentation/rpmsg.txt index a95e36a43288..24b7a9e1a5f9 100644 --- a/Documentation/rpmsg.txt +++ b/Documentation/rpmsg.txt @@ -1,10 +1,15 @@ +============================================ 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 @@ -58,170 +63,222 @@ to their destination address (this is done by invoking the driver's rx handler 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); @@ -234,32 +291,35 @@ static int rpmsg_sample_probe(struct rpmsg_channel *rpdev) } 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. |