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