1==========================================================================
2RapidIO subsystem Channelized Messaging character device driver (rio_cm.c)
3==========================================================================
4
5
61. Overview
7===========
8
9This device driver is the result of collaboration within the RapidIO.org
10Software Task Group (STG) between Texas Instruments, Prodrive Technologies,
11Nokia Networks, BAE and IDT.  Additional input was received from other members
12of RapidIO.org.
13
14The objective was to create a character mode driver interface which exposes
15messaging capabilities of RapidIO endpoint devices (mports) directly
16to applications, in a manner that allows the numerous and varied RapidIO
17implementations to interoperate.
18
19This driver (RIO_CM) provides to user-space applications shared access to
20RapidIO mailbox messaging resources.
21
22RapidIO specification (Part 2) defines that endpoint devices may have up to four
23messaging mailboxes in case of multi-packet message (up to 4KB) and
24up to 64 mailboxes if single-packet messages (up to 256 B) are used. In addition
25to protocol definition limitations, a particular hardware implementation can
26have reduced number of messaging mailboxes.  RapidIO aware applications must
27therefore share the messaging resources of a RapidIO endpoint.
28
29Main purpose of this device driver is to provide RapidIO mailbox messaging
30capability to large number of user-space processes by introducing socket-like
31operations using a single messaging mailbox.  This allows applications to
32use the limited RapidIO messaging hardware resources efficiently.
33
34Most of device driver's operations are supported through 'ioctl' system calls.
35
36When loaded this device driver creates a single file system node named rio_cm
37in /dev directory common for all registered RapidIO mport devices.
38
39Following ioctl commands are available to user-space applications:
40
41- RIO_CM_MPORT_GET_LIST:
42    Returns to caller list of local mport devices that
43    support messaging operations (number of entries up to RIO_MAX_MPORTS).
44    Each list entry is combination of mport's index in the system and RapidIO
45    destination ID assigned to the port.
46- RIO_CM_EP_GET_LIST_SIZE:
47    Returns number of messaging capable remote endpoints
48    in a RapidIO network associated with the specified mport device.
49- RIO_CM_EP_GET_LIST:
50    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:
54    Creates RapidIO message exchange channel data structure
55    with channel ID assigned automatically or as requested by a caller.
56- RIO_CM_CHAN_BIND:
57    Binds the specified channel data structure to the specified
58    mport device.
59- RIO_CM_CHAN_LISTEN:
60    Enables listening for connection requests on the specified
61    channel.
62- RIO_CM_CHAN_ACCEPT:
63    Accepts a connection request from peer on the specified
64    channel. If wait timeout for this request is specified by a caller it is
65    a blocking call. If timeout set to 0 this is non-blocking call - ioctl
66    handler checks for a pending connection request and if one is not available
67    exits with -EGAIN error status immediately.
68- RIO_CM_CHAN_CONNECT:
69    Sends a connection request to a remote peer/channel.
70- RIO_CM_CHAN_SEND:
71    Sends a data message through the specified channel.
72    The handler for this request assumes that message buffer specified by
73    a caller includes the reserved space for a packet header required by
74    this driver.
75- RIO_CM_CHAN_RECEIVE:
76    Receives a data message through a connected channel.
77    If the channel does not have an incoming message ready to return this ioctl
78    handler will wait for new message until timeout specified by a caller
79    expires. If timeout value is set to 0, ioctl handler uses a default value
80    defined by MAX_SCHEDULE_TIMEOUT.
81- RIO_CM_CHAN_CLOSE:
82    Closes a specified channel and frees associated buffers.
83    If the specified channel is in the CONNECTED state, sends close notification
84    to the remote peer.
85
86The ioctl command codes and corresponding data structures intended for use by
87user-space applications are defined in 'include/uapi/linux/rio_cm_cdev.h'.
88
892. Hardware Compatibility
90=========================
91
92This device driver uses standard interfaces defined by kernel RapidIO subsystem
93and therefore it can be used with any mport device driver registered by RapidIO
94subsystem with limitations set by available mport HW implementation of messaging
95mailboxes.
96
973. Module parameters
98====================
99
100- 'dbg_level'
101      - This parameter allows to control amount of debug information
102        generated by this device driver. This parameter is formed by set of
103        bit masks that correspond to the specific functional block.
104        For mask definitions see 'drivers/rapidio/devices/rio_cm.c'
105        This parameter can be changed dynamically.
106        Use CONFIG_RAPIDIO_DEBUG=y to enable debug output at the top level.
107
108- 'cmbox'
109      - Number of RapidIO mailbox to use (default value is 1).
110        This parameter allows to set messaging mailbox number that will be used
111        within entire RapidIO network. It can be used when default mailbox is
112        used by other device drivers or is not supported by some nodes in the
113        RapidIO network.
114
115- 'chstart'
116      - Start channel number for dynamic assignment. Default value - 256.
117        Allows to exclude channel numbers below this parameter from dynamic
118        allocation to avoid conflicts with software components that use
119        reserved predefined channel numbers.
120
1214. Known problems
122=================
123
124  None.
125
1265. User-space Applications and API Library
127==========================================
128
129Messaging API library and applications that use this device driver are available
130from RapidIO.org.
131
1326. TODO List
133============
134
135- Add support for system notification messages (reserved channel 0).
136