userfaultfd: replace ENOSPC with ESRCH in case mm has gone during copy/zeropage

[karo-tx-linux.git] / Documentation / rpmsg.txt

diff --git a/Documentation/rpmsg.txt b/Documentation/rpmsg.txt
index a95e36a43288fee73706c7202caa1c355b0b76c3..24b7a9e1a5f99695e6f74d1f79694a999271f903 100644 (file)
--- a/Documentation/rpmsg.txt
+++ b/Documentation/rpmsg.txt
@@ -1,10 +1,15 @@
+============================================

 Remote Processor Messaging (rpmsg) Framework
 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
 
 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).
 
 
 with the payload of the inbound message).
 
 

-2. User API
+User API
+========
+
+::

 
   int rpmsg_send(struct rpmsg_channel *rpdev, void *data, int len);
 
   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);
 
   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);
 
   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);
 
   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)
 
   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);
 
   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);
 
   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);
 
   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);
 
   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);
 
   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.
 
 
 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)
                                                void *priv, u32 src)

-{
+  {

        print_hex_dump(KERN_INFO, "incoming message:", DUMP_PREFIX_NONE,
                                                16, 1, data, len, true);
        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);
        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;
        }
 
        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");
        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" },
        { },
        { .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,
        .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.
 
 
 At this point we only support dynamic allocations of rpmsg channels.