1What:		/dev/fw[0-9]+
2Date:		May 2007
3KernelVersion:	2.6.22
4Contact:	linux1394-devel@lists.sourceforge.net
5Description:
6		The character device files /dev/fw* are the interface between
7		firewire-core and IEEE 1394 device drivers implemented in
8		userspace.  The ioctl(2)- and read(2)-based ABI is defined and
9		documented in <linux/firewire-cdev.h>.
10
11		This ABI offers most of the features which firewire-core also
12		exposes to kernelspace IEEE 1394 drivers.
13
14		Each /dev/fw* is associated with one IEEE 1394 node, which can
15		be remote or local nodes.  Operations on a /dev/fw* file have
16		different scope:
17		  - The 1394 node which is associated with the file:
18			  - Asynchronous request transmission
19			  - Get the Configuration ROM
20			  - Query node ID
21			  - Query maximum speed of the path between this node
22			    and local node
23		  - The 1394 bus (i.e. "card") to which the node is attached to:
24			  - Isochronous stream transmission and reception
25			  - Asynchronous stream transmission and reception
26			  - Asynchronous broadcast request transmission
27			  - PHY packet transmission and reception
28			  - Allocate, reallocate, deallocate isochronous
29			    resources (channels, bandwidth) at the bus's IRM
30			  - Query node IDs of local node, root node, IRM, bus
31			    manager
32			  - Query cycle time
33			  - Bus reset initiation, bus reset event reception
34		  - All 1394 buses:
35			  - Allocation of IEEE 1212 address ranges on the local
36			    link layers, reception of inbound requests to such
37			    an address range, asynchronous response transmission
38			    to inbound requests
39			  - Addition of descriptors or directories to the local
40			    nodes' Configuration ROM
41
42		Due to the different scope of operations and in order to let
43		userland implement different access permission models, some
44		operations are restricted to /dev/fw* files that are associated
45		with a local node:
46			  - Addition of descriptors or directories to the local
47			    nodes' Configuration ROM
48			  - PHY packet transmission and reception
49
50		A /dev/fw* file remains associated with one particular node
51		during its entire life time.  Bus topology changes, and hence
52		node ID changes, are tracked by firewire-core.  ABI users do not
53		need to be aware of topology.
54
55		The following file operations are supported:
56
57		open(2)
58		Currently the only useful flags are O_RDWR.
59
60		ioctl(2)
61		Initiate various actions.  Some take immediate effect, others
62		are performed asynchronously while or after the ioctl returns.
63		See the inline documentation in <linux/firewire-cdev.h> for
64		descriptions of all ioctls.
65
66		poll(2), select(2), epoll_wait(2) etc.
67		Watch for events to become available to be read.
68
69		read(2)
70		Receive various events.  There are solicited events like
71		outbound asynchronous transaction completion or isochronous
72		buffer completion, and unsolicited events such as bus resets,
73		request reception, or PHY packet reception.  Always use a read
74		buffer which is large enough to receive the largest event that
75		could ever arrive.  See <linux/firewire-cdev.h> for descriptions
76		of all event types and for which ioctls affect reception of
77		events.
78
79		mmap(2)
80		Allocate a DMA buffer for isochronous reception or transmission
81		and map it into the process address space.  The arguments should
82		be used as follows:  addr = NULL, length = the desired buffer
83		size, i.e. number of packets times size of largest packet,
84		prot = at least PROT_READ for reception and at least PROT_WRITE
85		for transmission, flags = MAP_SHARED, fd = the handle to the
86		/dev/fw*, offset = 0.
87
88		Isochronous reception works in packet-per-buffer fashion except
89		for multichannel reception which works in buffer-fill mode.
90
91		munmap(2)
92		Unmap the isochronous I/O buffer from the process address space.
93
94		close(2)
95		Besides stopping and freeing I/O contexts that were associated
96		with the file descriptor, back out any changes to the local
97		nodes' Configuration ROM.  Deallocate isochronous channels and
98		bandwidth at the IRM that were marked for kernel-assisted
99		re- and deallocation.
100
101Users:		libraw1394
102		libdc1394
103		libhinawa
104		tools like linux-firewire-utils, fwhack, ...
105