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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, ...