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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 | What: /dev/fw[0-9]+ Date: May 2007 KernelVersion: 2.6.22 Contact: linux1394-devel@lists.sourceforge.net Description: The character device files /dev/fw* are the interface between firewire-core and IEEE 1394 device drivers implemented in userspace. The ioctl(2)- and read(2)-based ABI is defined and documented in <linux/firewire-cdev.h>. This ABI offers most of the features which firewire-core also exposes to kernelspace IEEE 1394 drivers. Each /dev/fw* is associated with one IEEE 1394 node, which can be remote or local nodes. Operations on a /dev/fw* file have different scope: - The 1394 node which is associated with the file: - Asynchronous request transmission - Get the Configuration ROM - Query node ID - Query maximum speed of the path between this node and local node - The 1394 bus (i.e. "card") to which the node is attached to: - Isochronous stream transmission and reception - Asynchronous stream transmission and reception - Asynchronous broadcast request transmission - PHY packet transmission and reception - Allocate, reallocate, deallocate isochronous resources (channels, bandwidth) at the bus's IRM - Query node IDs of local node, root node, IRM, bus manager - Query cycle time - Bus reset initiation, bus reset event reception - All 1394 buses: - Allocation of IEEE 1212 address ranges on the local link layers, reception of inbound requests to such an address range, asynchronous response transmission to inbound requests - Addition of descriptors or directories to the local nodes' Configuration ROM Due to the different scope of operations and in order to let userland implement different access permission models, some operations are restricted to /dev/fw* files that are associated with a local node: - Addition of descriptors or directories to the local nodes' Configuration ROM - PHY packet transmission and reception A /dev/fw* file remains associated with one particular node during its entire life time. Bus topology changes, and hence node ID changes, are tracked by firewire-core. ABI users do not need to be aware of topology. The following file operations are supported: open(2) Currently the only useful flags are O_RDWR. ioctl(2) Initiate various actions. Some take immediate effect, others are performed asynchronously while or after the ioctl returns. See the inline documentation in <linux/firewire-cdev.h> for descriptions of all ioctls. poll(2), select(2), epoll_wait(2) etc. Watch for events to become available to be read. read(2) Receive various events. There are solicited events like outbound asynchronous transaction completion or isochronous buffer completion, and unsolicited events such as bus resets, request reception, or PHY packet reception. Always use a read buffer which is large enough to receive the largest event that could ever arrive. See <linux/firewire-cdev.h> for descriptions of all event types and for which ioctls affect reception of events. mmap(2) Allocate a DMA buffer for isochronous reception or transmission and map it into the process address space. The arguments should be used as follows: addr = NULL, length = the desired buffer size, i.e. number of packets times size of largest packet, prot = at least PROT_READ for reception and at least PROT_WRITE for transmission, flags = MAP_SHARED, fd = the handle to the /dev/fw*, offset = 0. Isochronous reception works in packet-per-buffer fashion except for multichannel reception which works in buffer-fill mode. munmap(2) Unmap the isochronous I/O buffer from the process address space. close(2) Besides stopping and freeing I/O contexts that were associated with the file descriptor, back out any changes to the local nodes' Configuration ROM. Deallocate isochronous channels and bandwidth at the IRM that were marked for kernel-assisted re- and deallocation. Users: libraw1394 libdc1394 tools like jujuutils, fwhack, ... |