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