diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-rpmsg | 75 | ||||
| -rw-r--r-- | Documentation/remoteproc.txt | 322 | ||||
| -rw-r--r-- | Documentation/rpmsg.txt | 293 |
3 files changed, 690 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-rpmsg b/Documentation/ABI/testing/sysfs-bus-rpmsg new file mode 100644 index 0000000..189e419 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-rpmsg @@ -0,0 +1,75 @@ +What: /sys/bus/rpmsg/devices/.../name +Date: June 2011 +KernelVersion: 3.3 +Contact: Ohad Ben-Cohen <ohad@wizery.com> +Description: + Every rpmsg device is a communication channel with a remote + processor. Channels are identified with a (textual) name, + which is maximum 32 bytes long (defined as RPMSG_NAME_SIZE in + rpmsg.h). + + This sysfs entry contains the name of this channel. + +What: /sys/bus/rpmsg/devices/.../src +Date: June 2011 +KernelVersion: 3.3 +Contact: Ohad Ben-Cohen <ohad@wizery.com> +Description: + Every rpmsg device is a communication channel with a remote + processor. Channels have a local ("source") rpmsg address, + and remote ("destination") rpmsg address. When an entity + starts listening on one end of a channel, it assigns it with + a unique rpmsg address (a 32 bits integer). This way when + inbound messages arrive to this address, the rpmsg core + dispatches them to the listening entity (a kernel driver). + + This sysfs entry contains the src (local) rpmsg address + of this channel. If it contains 0xffffffff, then an address + wasn't assigned (can happen if no driver exists for this + channel). + +What: /sys/bus/rpmsg/devices/.../dst +Date: June 2011 +KernelVersion: 3.3 +Contact: Ohad Ben-Cohen <ohad@wizery.com> +Description: + Every rpmsg device is a communication channel with a remote + processor. Channels have a local ("source") rpmsg address, + and remote ("destination") rpmsg address. When an entity + starts listening on one end of a channel, it assigns it with + a unique rpmsg address (a 32 bits integer). This way when + inbound messages arrive to this address, the rpmsg core + dispatches them to the listening entity. + + This sysfs entry contains the dst (remote) rpmsg address + of this channel. If it contains 0xffffffff, then an address + wasn't assigned (can happen if the kernel driver that + is attached to this channel is exposing a service to the + remote processor. This make it a local rpmsg server, + and it is listening for inbound messages that may be sent + from any remote rpmsg client; it is not bound to a single + remote entity). + +What: /sys/bus/rpmsg/devices/.../announce +Date: June 2011 +KernelVersion: 3.3 +Contact: Ohad Ben-Cohen <ohad@wizery.com> +Description: + Every rpmsg device is a communication channel with a remote + processor. Channels are identified by a textual name (see + /sys/bus/rpmsg/devices/.../name above) and have a local + ("source") rpmsg address, and remote ("destination") rpmsg + address. + + A channel is first created when an entity, whether local + or remote, starts listening on it for messages (and is thus + called an rpmsg server). + + When that happens, a "name service" announcement is sent + to the other processor, in order to let it know about the + creation of the channel (this way remote clients know they + can start sending messages). + + This sysfs entry tells us whether the channel is a local + server channel that is announced (values are either + true or false). diff --git a/Documentation/remoteproc.txt b/Documentation/remoteproc.txt new file mode 100644 index 0000000..70a048c --- /dev/null +++ b/Documentation/remoteproc.txt @@ -0,0 +1,322 @@ +Remote Processor Framework + +1. Introduction + +Modern SoCs typically have heterogeneous remote processor devices in asymmetric +multiprocessing (AMP) configurations, which may be running different instances +of operating system, whether it's Linux or any other flavor of real-time OS. + +OMAP4, for example, has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP. +In a typical configuration, the dual cortex-A9 is running Linux in a SMP +configuration, and each of the other three cores (two M3 cores and a DSP) +is running its own instance of RTOS in an AMP configuration. + +The remoteproc framework allows different platforms/architectures to +control (power on, load firmware, power off) those remote processors while +abstracting the hardware differences, so the entire driver doesn't need to be +duplicated. In addition, this framework also adds rpmsg virtio devices +for remote processors that supports this kind of communication. This way, +platform-specific remoteproc drivers only need to provide a few low-level +handlers, and then all rpmsg drivers will then just work +(for more information about the virtio-based rpmsg bus and its drivers, +please read Documentation/rpmsg.txt). +Registration of other types of virtio devices is now also possible. Firmwares +just need to publish what kind of virtio devices do they support, and then +remoteproc will add those devices. This makes it possible to reuse the +existing virtio drivers with remote processor backends at a minimal development +cost. + +2. User API + + int rproc_boot(struct rproc *rproc) + - Boot a remote processor (i.e. load its firmware, power it on, ...). + If the remote processor is already powered on, this function immediately + returns (successfully). + Returns 0 on success, and an appropriate error value otherwise. + Note: to use this function you should already have a valid rproc + handle. There are several ways to achieve that cleanly (devres, pdata, + the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we + might also consider using dev_archdata for this). See also + rproc_get_by_name() below. + + void rproc_shutdown(struct rproc *rproc) + - Power off a remote processor (previously booted with rproc_boot()). + In case @rproc is still being used by an additional user(s), then + this function will just decrement the power refcount and exit, + without really powering off the device. + Every call to rproc_boot() must (eventually) be accompanied by a call + to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug. + Notes: + - we're not decrementing the rproc's refcount, only the power refcount. + which means that the @rproc handle stays valid even after + rproc_shutdown() returns, and users can still use it with a subsequent + rproc_boot(), if needed. + - don't call rproc_shutdown() to unroll rproc_get_by_name(), exactly + because rproc_shutdown() _does not_ decrement the refcount of @rproc. + To decrement the refcount of @rproc, use rproc_put() (but _only_ if + you acquired @rproc using rproc_get_by_name()). + + struct rproc *rproc_get_by_name(const char *name) + - Find an rproc handle using the remote processor's name, and then + boot it. If it's already powered on, then just immediately return + (successfully). Returns the rproc handle on success, and NULL on failure. + This function increments the remote processor's refcount, so always + use rproc_put() to decrement it back once rproc isn't needed anymore. + Note: currently rproc_get_by_name() and rproc_put() are not used anymore + by the rpmsg bus and its drivers. We need to scrutinize the use cases + that still need them, and see if we can migrate them to use the non + name-based boot/shutdown interface. + + void rproc_put(struct rproc *rproc) + - Decrement @rproc's power refcount and shut it down if it reaches zero + (essentially by just calling rproc_shutdown), and then decrement @rproc's + validity refcount too. + After this function returns, @rproc may _not_ be used anymore, and its + handle should be considered invalid. + This function should be called _iff_ the @rproc handle was grabbed by + calling rproc_get_by_name(). + +3. Typical usage + +#include <linux/remoteproc.h> + +/* in case we were given a valid 'rproc' handle */ +int dummy_rproc_example(struct rproc *my_rproc) +{ + int ret; + + /* let's power on and boot our remote processor */ + ret = rproc_boot(my_rproc); + if (ret) { + /* + * something went wrong. handle it and leave. + */ + } + + /* + * our remote processor is now powered on... give it some work + */ + + /* let's shut it down now */ + rproc_shutdown(my_rproc); +} + +4. API for implementors + + struct rproc *rproc_alloc(struct device *dev, const char *name, + const struct rproc_ops *ops, + const char *firmware, int len) + - Allocate a new remote processor handle, but don't register + it yet. Required parameters are the underlying device, the + name of this remote processor, platform-specific ops handlers, + the name of the firmware to boot this rproc with, and the + length of private data needed by the allocating rproc driver (in bytes). + + This function should be used by rproc implementations during + initialization of the remote processor. + After creating an rproc handle using this function, and when ready, + implementations should then call rproc_register() to complete + the registration of the remote processor. + On success, the new rproc is returned, and on failure, NULL. + + Note: _never_ directly deallocate @rproc, even if it was not registered + yet. Instead, if you just need to unroll rproc_alloc(), use rproc_free(). + + void rproc_free(struct rproc *rproc) + - Free an rproc handle that was allocated by rproc_alloc. + This function should _only_ be used if @rproc was only allocated, + but not registered yet. + If @rproc was already successfully registered (by calling + rproc_register()), then use rproc_unregister() instead. + + int rproc_register(struct rproc *rproc) + - Register @rproc with the remoteproc framework, after it has been + allocated with rproc_alloc(). + This is called by the platform-specific rproc implementation, whenever + a new remote processor device is probed. + Returns 0 on success and an appropriate error code otherwise. + Note: this function initiates an asynchronous firmware loading + context, which will look for virtio devices supported by the rproc's + firmware. + If found, those virtio devices will be created and added, so as a result + of registering this remote processor, additional virtio drivers might get + probed. + + int rproc_unregister(struct rproc *rproc) + - Unregister a remote processor, and decrement its refcount. + If its refcount drops to zero, then @rproc will be freed. If not, + it will be freed later once the last reference is dropped. + + This function should be called when the platform specific rproc + implementation decides to remove the rproc device. it should + _only_ be called if a previous invocation of rproc_register() + has completed successfully. + + After rproc_unregister() returns, @rproc is _not_ valid anymore and + it shouldn't be used. More specifically, don't call rproc_free() + or try to directly free @rproc after rproc_unregister() returns; + none of these are needed, and calling them is a bug. + + Returns 0 on success and -EINVAL if @rproc isn't valid. + +5. Implementation callbacks + +These callbacks should be provided by platform-specific remoteproc +drivers: + +/** + * struct rproc_ops - platform-specific device handlers + * @start: power on the device and boot it + * @stop: power off the device + * @kick: kick a virtqueue (virtqueue id given as a parameter) + */ +struct rproc_ops { + int (*start)(struct rproc *rproc); + int (*stop)(struct rproc *rproc); + void (*kick)(struct rproc *rproc, int vqid); +}; + +Every remoteproc implementation should at least provide the ->start and ->stop +handlers. If rpmsg/virtio functionality is also desired, then the ->kick handler +should be provided as well. + +The ->start() handler takes an rproc handle and should then power on the +device and boot it (use rproc->priv to access platform-specific private data). +The boot address, in case needed, can be found in rproc->bootaddr (remoteproc +core puts there the ELF entry point). +On success, 0 should be returned, and on failure, an appropriate error code. + +The ->stop() handler takes an rproc handle and powers the device down. +On success, 0 is returned, and on failure, an appropriate error code. + +The ->kick() handler takes an rproc handle, and an index of a virtqueue +where new message was placed in. Implementations should interrupt the remote +processor and let it know it has pending messages. Notifying remote processors +the exact virtqueue index to look in is optional: it is easy (and not +too expensive) to go through the existing virtqueues and look for new buffers +in the used rings. + +6. Binary Firmware Structure + +At this point remoteproc only supports ELF32 firmware binaries. However, +it is quite expected that other platforms/devices which we'd want to +support with this framework will be based on different binary formats. + +When those use cases show up, we will have to decouple the binary format +from the framework core, so we can support several binary formats without +duplicating common code. + +When the firmware is parsed, its various segments are loaded to memory +according to the specified device address (might be a physical address +if the remote processor is accessing memory directly). + +In addition to the standard ELF segments, most remote processors would +also include a special section which we call "the resource table". + +The resource table contains system resources that the remote processor +requires before it should be powered on, such as allocation of physically +contiguous memory, or iommu mapping of certain on-chip peripherals. +Remotecore will only power up the device after all the resource table's +requirement are met. + +In addition to system resources, the resource table may also contain +resource entries that publish the existence of supported features +or configurations by the remote processor, such as trace buffers and +supported virtio devices (and their configurations). + +The resource table begins with this header: + +/** + * struct resource_table - firmware resource table header + * @ver: version number + * @num: number of resource entries + * @reserved: reserved (must be zero) + * @offset: array of offsets pointing at the various resource entries + * + * The header of the resource table, as expressed by this structure, + * contains a version number (should we need to change this format in the + * future), the number of available resource entries, and their offsets + * in the table. + */ +struct resource_table { + u32 ver; + u32 num; + u32 reserved[2]; + u32 offset[0]; +} __packed; + +Immediately following this header are the resource entries themselves, +each of which begins with the following resource entry header: + +/** + * struct fw_rsc_hdr - firmware resource entry header + * @type: resource type + * @data: resource data + * + * Every resource entry begins with a 'struct fw_rsc_hdr' header providing + * its @type. The content of the entry itself will immediately follow + * this header, and it should be parsed according to the resource type. + */ +struct fw_rsc_hdr { + u32 type; + u8 data[0]; +} __packed; + +Some resources entries are mere announcements, where the host is informed +of specific remoteproc configuration. Other entries require the host to +do something (e.g. allocate a system resource). Sometimes a negotiation +is expected, where the firmware requests a resource, and once allocated, +the host should provide back its details (e.g. address of an allocated +memory region). + +Here are the various resource types that are currently supported: + +/** + * enum fw_resource_type - types of resource entries + * + * @RSC_CARVEOUT: request for allocation of a physically contiguous + * memory region. + * @RSC_DEVMEM: request to iommu_map a memory-based peripheral. + * @RSC_TRACE: announces the availability of a trace buffer into which + * the remote processor will be writing logs. + * @RSC_VDEV: declare support for a virtio device, and serve as its + * virtio header. + * @RSC_LAST: just keep this one at the end + * + * Please note that these values are used as indices to the rproc_handle_rsc + * lookup table, so please keep them sane. Moreover, @RSC_LAST is used to + * check the validity of an index before the lookup table is accessed, so + * please update it as needed. + */ +enum fw_resource_type { + RSC_CARVEOUT = 0, + RSC_DEVMEM = 1, + RSC_TRACE = 2, + RSC_VDEV = 3, + RSC_LAST = 4, +}; + +For more details regarding a specific resource type, please see its +dedicated structure in include/linux/remoteproc.h. + +We also expect that platform-specific resource entries will show up +at some point. When that happens, we could easily add a new RSC_PLATFORM +type, and hand those resources to the platform-specific rproc driver to handle. + +7. Virtio and remoteproc + +The firmware should provide remoteproc information about virtio devices +that it supports, and their configurations: a RSC_VDEV resource entry +should specify the virtio device id (as in virtio_ids.h), virtio features, +virtio config space, vrings information, etc. + +When a new remote processor is registered, the remoteproc framework +will look for its resource table and will register the virtio devices +it supports. A firmware may support any number of virtio devices, and +of any type (a single remote processor can also easily support several +rpmsg virtio devices this way, if desired). + +Of course, RSC_VDEV resource entries are only good enough for static +allocation of virtio devices. Dynamic allocations will also be made possible +using the rpmsg bus (similar to how we already do dynamic allocations of +rpmsg channels; read more about it in rpmsg.txt). diff --git a/Documentation/rpmsg.txt b/Documentation/rpmsg.txt new file mode 100644 index 0000000..409d9f9 --- /dev/null +++ b/Documentation/rpmsg.txt @@ -0,0 +1,293 @@ +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/). + +1. Introduction + +Modern SoCs typically employ heterogeneous remote processor devices in +asymmetric multiprocessing (AMP) configurations, which may be running +different instances of operating system, whether it's Linux or any other +flavor of real-time OS. + +OMAP4, for example, has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP. +Typically, the dual cortex-A9 is running Linux in a SMP configuration, +and each of the other three cores (two M3 cores and a DSP) is running +its own instance of RTOS in an AMP configuration. + +Typically AMP remote processors employ dedicated DSP codecs and multimedia +hardware accelerators, and therefore are often used to offload CPU-intensive +multimedia tasks from the main application processor. + +These remote processors could also be used to control latency-sensitive +sensors, drive random hardware blocks, or just perform background tasks +while the main CPU is idling. + +Users of those remote processors can either be userland apps (e.g. multimedia +frameworks talking with remote OMX components) or kernel drivers (controlling +hardware accessible only by the remote processor, reserving kernel-controlled +resources on behalf of the remote processor, etc..). + +Rpmsg is a virtio-based messaging bus that allows kernel drivers to communicate +with remote processors available on the system. In turn, drivers could then +expose appropriate user space interfaces, if needed. + +When writing a driver that exposes rpmsg communication to userland, please +keep in mind that remote processors might have direct access to the +system's physical memory and other sensitive hardware resources (e.g. on +OMAP4, remote cores and hardware accelerators may have direct access to the +physical memory, gpio banks, dma controllers, i2c bus, gptimers, mailbox +devices, hwspinlocks, etc..). Moreover, those remote processors might be +running RTOS where every task can access the entire memory/devices exposed +to the processor. To minimize the risks of rogue (or buggy) userland code +exploiting remote bugs, and by that taking over the system, it is often +desired to limit userland to specific rpmsg channels (see definition below) +it can send messages on, and if possible, minimize how much control +it has over the content of the messages. + +Every rpmsg device is a communication channel with a remote processor (thus +rpmsg devices are called channels). Channels are identified by a textual name +and have a local ("source") rpmsg address, and remote ("destination") rpmsg +address. + +When a driver starts listening on a channel, its rx callback is bound with +a unique rpmsg local address (a 32-bit integer). This way when inbound messages +arrive, the rpmsg core dispatches them to the appropriate driver according +to their destination address (this is done by invoking the driver's rx handler +with the payload of the inbound message). + + +2. 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. + + 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. + + 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. + + 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. + + 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. + + 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. + + 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. + + 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(). + + 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. + + 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 + +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> + +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) +{ + int err; + + dev_info(&rpdev->dev, "chnl: 0x%x -> 0x%x\n", rpdev->src, rpdev->dst); + + /* send a message on our channel */ + err = rpmsg_send(rpdev, "hello!", 6); + if (err) { + pr_err("rpmsg_send failed: %d\n", err); + return err; + } + + return 0; +} + +static void __devexit 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[] = { + { .name = "rpmsg-client-sample" }, + { }, +}; +MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_sample_id_table); + +static struct rpmsg_driver rpmsg_sample_client = { + .drv.name = KBUILD_MODNAME, + .drv.owner = THIS_MODULE, + .id_table = rpmsg_driver_sample_id_table, + .probe = rpmsg_sample_probe, + .callback = rpmsg_sample_cb, + .remove = __devexit_p(rpmsg_sample_remove), +}; + +static int __init init(void) +{ + return register_rpmsg_driver(&rpmsg_sample_client); +} +module_init(init); + +static void __exit fini(void) +{ + unregister_rpmsg_driver(&rpmsg_sample_client); +} +module_exit(fini); + +Note: a similar sample which can be built and loaded can be found +in samples/rpmsg/. + +4. Allocations of rpmsg channels: + +At this point we only support dynamic allocations of rpmsg channels. + +This is possible only with remote processors that have the VIRTIO_RPMSG_F_NS +virtio device feature set. This feature bit means that the remote +processor supports dynamic name service announcement messages. + +When this feature is enabled, creation of rpmsg devices (i.e. channels) +is completely dynamic: the remote processor announces the existence of a +remote rpmsg service by sending a name service message (which contains +the name and rpmsg addr of the remote service, see struct rpmsg_ns_msg). + +This message is then handled by the rpmsg bus, which in turn dynamically +creates and registers an rpmsg channel (which represents the remote service). +If/when a relevant rpmsg driver is registered, it will be immediately probed +by the bus, and can then start sending messages to the remote service. + +The plan is also to add static creation of rpmsg channels via the virtio +config space, but it's not implemented yet. |