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Alexandre Bounineb6e8d4a2016-08-02 14:06:25 -07001RapidIO 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).