About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / ABI / stable / firewire-cdev




Custom Search

Based on kernel version 3.16. Page generated on 2014-08-06 21:35 EST.

1	What:		/dev/fw[0-9]+
2	Date:		May 2007
3	KernelVersion:	2.6.22
4	Contact:	linux1394-devel@lists.sourceforge.net
5	Description:
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	
101	Users:		libraw1394
102			libdc1394
103			tools like jujuutils, fwhack, ...
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.