1RapidIO subsystem Channelized Messaging character device driver (rio_cm.c)
2==========================================================================
3
4Version History:
5----------------
6  1.0.0 - Initial driver release.
7
8==========================================================================
9
10I. Overview
11
12This device driver is the result of collaboration within the RapidIO.org
13Software Task Group (STG) between Texas Instruments, Prodrive Technologies,
14Nokia Networks, BAE and IDT.  Additional input was received from other members
15of RapidIO.org.
16
17The objective was to create a character mode driver interface which exposes
18messaging capabilities of RapidIO endpoint devices (mports) directly
19to applications, in a manner that allows the numerous and varied RapidIO
20implementations to interoperate.
21
22This driver (RIO_CM) provides to user-space applications shared access to
23RapidIO mailbox messaging resources.
24
25RapidIO specification (Part 2) defines that endpoint devices may have up to four
26messaging mailboxes in case of multi-packet message (up to 4KB) and
27up to 64 mailboxes if single-packet messages (up to 256 B) are used. In addition
28to protocol definition limitations, a particular hardware implementation can
29have reduced number of messaging mailboxes.  RapidIO aware applications must
30therefore share the messaging resources of a RapidIO endpoint.
31
32Main purpose of this device driver is to provide RapidIO mailbox messaging
33capability to large number of user-space processes by introducing socket-like
34operations using a single messaging mailbox.  This allows applications to
35use the limited RapidIO messaging hardware resources efficiently.
36
37Most of device driver's operations are supported through 'ioctl' system calls.
38
39When loaded this device driver creates a single file system node named rio_cm
40in /dev directory common for all registered RapidIO mport devices.
41
42Following ioctl commands are available to user-space applications:
43
44- RIO_CM_MPORT_GET_LIST : Returns to caller list of local mport devices that
45    support messaging operations (number of entries up to RIO_MAX_MPORTS).
46    Each list entry is combination of mport's index in the system and RapidIO
47    destination ID assigned to the port.
48- RIO_CM_EP_GET_LIST_SIZE : Returns number of messaging capable remote endpoints
49    in a RapidIO network associated with the specified mport device.
50- RIO_CM_EP_GET_LIST : Returns list of RapidIO destination IDs for messaging
51    capable remote endpoints (peers) available in a RapidIO network associated
52    with the specified mport device.
53- RIO_CM_CHAN_CREATE : Creates RapidIO message exchange channel data structure
54    with channel ID assigned automatically or as requested by a caller.
55- RIO_CM_CHAN_BIND : Binds the specified channel data structure to the specified
56    mport device.
57- RIO_CM_CHAN_LISTEN : Enables listening for connection requests on the specified
58    channel.
59- RIO_CM_CHAN_ACCEPT : Accepts a connection request from peer on the specified
60    channel. If wait timeout for this request is specified by a caller it is
61    a blocking call. If timeout set to 0 this is non-blocking call - ioctl
62    handler checks for a pending connection request and if one is not available
63    exits with -EGAIN error status immediately.
64- RIO_CM_CHAN_CONNECT : Sends a connection request to a remote peer/channel.
65- RIO_CM_CHAN_SEND : Sends a data message through the specified channel.
66    The handler for this request assumes that message buffer specified by
67    a caller includes the reserved space for a packet header required by
68    this driver.
69- RIO_CM_CHAN_RECEIVE : Receives a data message through a connected channel.
70    If the channel does not have an incoming message ready to return this ioctl
71    handler will wait for new message until timeout specified by a caller
72    expires. If timeout value is set to 0, ioctl handler uses a default value
73    defined by MAX_SCHEDULE_TIMEOUT.
74- RIO_CM_CHAN_CLOSE : Closes a specified channel and frees associated buffers.
75    If the specified channel is in the CONNECTED state, sends close notification
76    to the remote peer.
77
78The ioctl command codes and corresponding data structures intended for use by
79user-space applications are defined in 'include/uapi/linux/rio_cm_cdev.h'.
80
81II. Hardware Compatibility
82
83This device driver uses standard interfaces defined by kernel RapidIO subsystem
84and therefore it can be used with any mport device driver registered by RapidIO
85subsystem with limitations set by available mport HW implementation of messaging
86mailboxes.
87
88III. Module parameters
89
90- 'dbg_level' - This parameter allows to control amount of debug information
91        generated by this device driver. This parameter is formed by set of
92        bit masks that correspond to the specific functional block.
93        For mask definitions see 'drivers/rapidio/devices/rio_cm.c'
94        This parameter can be changed dynamically.
95        Use CONFIG_RAPIDIO_DEBUG=y to enable debug output at the top level.
96
97- 'cmbox' - Number of RapidIO mailbox to use (default value is 1).
98        This parameter allows to set messaging mailbox number that will be used
99        within entire RapidIO network. It can be used when default mailbox is
100        used by other device drivers or is not supported by some nodes in the
101        RapidIO network.
102
103- 'chstart' - Start channel number for dynamic assignment. Default value - 256.
104        Allows to exclude channel numbers below this parameter from dynamic
105        allocation to avoid conflicts with software components that use
106        reserved predefined channel numbers.
107
108IV. Known problems
109
110  None.
111
112V. User-space Applications and API Library
113
114Messaging API library and applications that use this device driver are available
115from RapidIO.org.
116
117VI. TODO List
118
119- Add support for system notification messages (reserved channel 0).
120