136 lines
5.8 KiB
ReStructuredText
136 lines
5.8 KiB
ReStructuredText
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==========================================================================
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RapidIO subsystem Channelized Messaging character device driver (rio_cm.c)
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==========================================================================
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1. Overview
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===========
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This device driver is the result of collaboration within the RapidIO.org
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Software Task Group (STG) between Texas Instruments, Prodrive Technologies,
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Nokia Networks, BAE and IDT. Additional input was received from other members
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of RapidIO.org.
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The objective was to create a character mode driver interface which exposes
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messaging capabilities of RapidIO endpoint devices (mports) directly
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to applications, in a manner that allows the numerous and varied RapidIO
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implementations to interoperate.
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This driver (RIO_CM) provides to user-space applications shared access to
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RapidIO mailbox messaging resources.
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RapidIO specification (Part 2) defines that endpoint devices may have up to four
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messaging mailboxes in case of multi-packet message (up to 4KB) and
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up to 64 mailboxes if single-packet messages (up to 256 B) are used. In addition
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to protocol definition limitations, a particular hardware implementation can
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have reduced number of messaging mailboxes. RapidIO aware applications must
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therefore share the messaging resources of a RapidIO endpoint.
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Main purpose of this device driver is to provide RapidIO mailbox messaging
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capability to large number of user-space processes by introducing socket-like
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operations using a single messaging mailbox. This allows applications to
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use the limited RapidIO messaging hardware resources efficiently.
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Most of device driver's operations are supported through 'ioctl' system calls.
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When loaded this device driver creates a single file system node named rio_cm
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in /dev directory common for all registered RapidIO mport devices.
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Following ioctl commands are available to user-space applications:
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- RIO_CM_MPORT_GET_LIST:
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Returns to caller list of local mport devices that
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support messaging operations (number of entries up to RIO_MAX_MPORTS).
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Each list entry is combination of mport's index in the system and RapidIO
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destination ID assigned to the port.
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- RIO_CM_EP_GET_LIST_SIZE:
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Returns number of messaging capable remote endpoints
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in a RapidIO network associated with the specified mport device.
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- RIO_CM_EP_GET_LIST:
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Returns list of RapidIO destination IDs for messaging
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capable remote endpoints (peers) available in a RapidIO network associated
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with the specified mport device.
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- RIO_CM_CHAN_CREATE:
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Creates RapidIO message exchange channel data structure
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with channel ID assigned automatically or as requested by a caller.
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- RIO_CM_CHAN_BIND:
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Binds the specified channel data structure to the specified
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mport device.
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- RIO_CM_CHAN_LISTEN:
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Enables listening for connection requests on the specified
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channel.
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- RIO_CM_CHAN_ACCEPT:
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Accepts a connection request from peer on the specified
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channel. If wait timeout for this request is specified by a caller it is
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a blocking call. If timeout set to 0 this is non-blocking call - ioctl
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handler checks for a pending connection request and if one is not available
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exits with -EGAIN error status immediately.
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- RIO_CM_CHAN_CONNECT:
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Sends a connection request to a remote peer/channel.
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- RIO_CM_CHAN_SEND:
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Sends a data message through the specified channel.
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The handler for this request assumes that message buffer specified by
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a caller includes the reserved space for a packet header required by
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this driver.
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- RIO_CM_CHAN_RECEIVE:
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Receives a data message through a connected channel.
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If the channel does not have an incoming message ready to return this ioctl
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handler will wait for new message until timeout specified by a caller
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expires. If timeout value is set to 0, ioctl handler uses a default value
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defined by MAX_SCHEDULE_TIMEOUT.
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- RIO_CM_CHAN_CLOSE:
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Closes a specified channel and frees associated buffers.
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If the specified channel is in the CONNECTED state, sends close notification
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to the remote peer.
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The ioctl command codes and corresponding data structures intended for use by
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user-space applications are defined in 'include/uapi/linux/rio_cm_cdev.h'.
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2. Hardware Compatibility
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=========================
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This device driver uses standard interfaces defined by kernel RapidIO subsystem
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and therefore it can be used with any mport device driver registered by RapidIO
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subsystem with limitations set by available mport HW implementation of messaging
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mailboxes.
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3. Module parameters
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====================
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- 'dbg_level'
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- This parameter allows to control amount of debug information
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generated by this device driver. This parameter is formed by set of
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bit masks that correspond to the specific functional block.
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For mask definitions see 'drivers/rapidio/devices/rio_cm.c'
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This parameter can be changed dynamically.
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Use CONFIG_RAPIDIO_DEBUG=y to enable debug output at the top level.
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- 'cmbox'
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- Number of RapidIO mailbox to use (default value is 1).
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This parameter allows to set messaging mailbox number that will be used
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within entire RapidIO network. It can be used when default mailbox is
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used by other device drivers or is not supported by some nodes in the
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RapidIO network.
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- 'chstart'
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- Start channel number for dynamic assignment. Default value - 256.
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Allows to exclude channel numbers below this parameter from dynamic
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allocation to avoid conflicts with software components that use
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reserved predefined channel numbers.
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4. Known problems
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=================
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None.
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5. User-space Applications and API Library
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==========================================
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Messaging API library and applications that use this device driver are available
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from RapidIO.org.
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6. TODO List
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============
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- Add support for system notification messages (reserved channel 0).
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