firewire: cdev: ABI documentation enhancements

Add overview documentation in Documentation/ABI/stable/firewire-cdev.

Improve the inline reference documentation in firewire-cdev.h:

  - Add /* available since kernel... */ comments to event numbers
    consistent with the comments on ioctl numbers.

  - Shorten some documentation on an event and an ioctl that are
    less interesting to current programming because there are newer
    preferable variants.

  - Spell Configuration ROM (name of an IEEE 1212 register) in
    upper case.

  - Move the dummy FW_CDEV_VERSION out of the reader's field of
    vision.  We should remove it from the header next year or so.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 103 insertions, 0 deletions

diff --git a/Documentation/ABI/stable/firewire-cdev b/Documentation/ABI/stable/firewire-cdev
new file mode 100644
index 000000000000..16d030827368
--- /dev/null
+++ b/Documentation/ABI/stable/firewire-cdev
@@ -0,0 +1,103 @@
+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, ...