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
18		  - The 1394 node which is associated with the file:
19
20			  - Asynchronous request transmission
21			  - Get the Configuration ROM
22			  - Query node ID
23			  - Query maximum speed of the path between this node
24			    and local node
25
26		  - The 1394 bus (i.e. "card") to which the node is attached to:
27
28			  - Isochronous stream transmission and reception
29			  - Asynchronous stream transmission and reception
30			  - Asynchronous broadcast request transmission
31			  - PHY packet transmission and reception
32			  - Allocate, reallocate, deallocate isochronous
33			    resources (channels, bandwidth) at the bus's IRM
34			  - Query node IDs of local node, root node, IRM, bus
35			    manager
36			  - Query cycle time
37			  - Bus reset initiation, bus reset event reception
38
39		  - All 1394 buses:
40
41			  - Allocation of IEEE 1212 address ranges on the local
42			    link layers, reception of inbound requests to such
43			    an address range, asynchronous response transmission
44			    to inbound requests
45			  - Addition of descriptors or directories to the local
46			    nodes' Configuration ROM
47
48		Due to the different scope of operations and in order to let
49		userland implement different access permission models, some
50		operations are restricted to /dev/fw* files that are associated
51		with a local node:
52
53			  - Addition of descriptors or directories to the local
54			    nodes' Configuration ROM
55			  - PHY packet transmission and reception
56
57		A /dev/fw* file remains associated with one particular node
58		during its entire life time.  Bus topology changes, and hence
59		node ID changes, are tracked by firewire-core.  ABI users do not
60		need to be aware of topology.
61
62		The following file operations are supported:
63
64		open(2)
65		    Currently the only useful flags are O_RDWR.
66
67		ioctl(2)
68		    Initiate various actions.  Some take immediate effect, others
69		    are performed asynchronously while or after the ioctl returns.
70		    See the inline documentation in <linux/firewire-cdev.h> for
71		    descriptions of all ioctls.
72
73		poll(2), select(2), epoll_wait(2) etc.
74		    Watch for events to become available to be read.
75
76		read(2)
77		    Receive various events.  There are solicited events like
78		    outbound asynchronous transaction completion or isochronous
79		    buffer completion, and unsolicited events such as bus resets,
80		    request reception, or PHY packet reception.  Always use a read
81		    buffer which is large enough to receive the largest event that
82		    could ever arrive.  See <linux/firewire-cdev.h> for descriptions
83		    of all event types and for which ioctls affect reception of
84		    events.
85
86		mmap(2)
87		    Allocate a DMA buffer for isochronous reception or transmission
88		    and map it into the process address space.  The arguments should
89		    be used as follows:  addr = NULL, length = the desired buffer
90		    size, i.e. number of packets times size of largest packet,
91		    prot = at least PROT_READ for reception and at least PROT_WRITE
92		    for transmission, flags = MAP_SHARED, fd = the handle to the
93		    /dev/fw*, offset = 0.
94
95		Isochronous reception works in packet-per-buffer fashion except
96		for multichannel reception which works in buffer-fill mode.
97
98		munmap(2)
99		    Unmap the isochronous I/O buffer from the process address space.
100
101		close(2)
102		    Besides stopping and freeing I/O contexts that were associated
103		    with the file descriptor, back out any changes to the local
104		    nodes' Configuration ROM.  Deallocate isochronous channels and
105		    bandwidth at the IRM that were marked for kernel-assisted
106		    re- and deallocation.
107
108Users:		libraw1394;
109		libdc1394;
110		libhinawa;
111		tools like linux-firewire-utils, fwhack, ...
112