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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>
This commit is contained in:
Stefan Richter 2011-07-14 21:08:39 +02:00
parent 93b37905f7
commit f6a7cd0212
2 changed files with 137 additions and 41 deletions
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103
Documentation/ABI/stable/firewire-cdev Normal file
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@ -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, ...

75
include/linux/firewire-cdev.h
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@ -30,10 +30,13 @@
#include <linux/types.h>
#include <linux/firewire-constants.h>
/* available since kernel version 2.6.22 */
#define FW_CDEV_EVENT_BUS_RESET 0x00
#define FW_CDEV_EVENT_RESPONSE 0x01
#define FW_CDEV_EVENT_REQUEST 0x02
#define FW_CDEV_EVENT_ISO_INTERRUPT 0x03
/* available since kernel version 2.6.30 */
#define FW_CDEV_EVENT_ISO_RESOURCE_ALLOCATED 0x04
#define FW_CDEV_EVENT_ISO_RESOURCE_DEALLOCATED 0x05
@ -120,24 +123,11 @@ struct fw_cdev_event_response {
/**
* struct fw_cdev_event_request - Old version of &fw_cdev_event_request2
* @closure: See &fw_cdev_event_common; set by %FW_CDEV_IOC_ALLOCATE ioctl
* @type: See &fw_cdev_event_common; always %FW_CDEV_EVENT_REQUEST
* @tcode: See &fw_cdev_event_request2
* @offset: See &fw_cdev_event_request2
* @handle: See &fw_cdev_event_request2
* @length: See &fw_cdev_event_request2
* @data: See &fw_cdev_event_request2
*
* This event is sent instead of &fw_cdev_event_request2 if the kernel or
* the client implements ABI version <= 3.
*
* Unlike &fw_cdev_event_request2, the sender identity cannot be established,
* broadcast write requests cannot be distinguished from unicast writes, and
* @tcode of lock requests is %TCODE_LOCK_REQUEST.
*
* Requests to the FCP_REQUEST or FCP_RESPONSE register are responded to as
* with &fw_cdev_event_request2, except in kernel 2.6.32 and older which send
* the response packet of the client's %FW_CDEV_IOC_SEND_RESPONSE ioctl.
* the client implements ABI version <= 3. &fw_cdev_event_request lacks
* essential information; use &fw_cdev_event_request2 instead.
*/
struct fw_cdev_event_request {
__u64 closure;
@ -452,30 +442,29 @@ union fw_cdev_event {
* %FW_CDEV_ISO_CONTEXT_RECEIVE_MULTICHANNEL, and
* %FW_CDEV_IOC_SET_ISO_CHANNELS
*/
#define FW_CDEV_VERSION 3 /* Meaningless; don't use this macro. */
/**
* struct fw_cdev_get_info - General purpose information ioctl
* @version: The version field is just a running serial number. Both an
* input parameter (ABI version implemented by the client) and
* output parameter (ABI version implemented by the kernel).
* A client must not fill in an %FW_CDEV_VERSION defined from an
* included kernel header file but the actual version for which
* the client was implemented. This is necessary for forward
* compatibility. We never break backwards compatibility, but
* may add more structs, events, and ioctls in later revisions.
* @rom_length: If @rom is non-zero, at most rom_length bytes of configuration
* A client shall fill in the ABI @version for which the client
* was implemented. This is necessary for forward compatibility.
* @rom_length: If @rom is non-zero, up to @rom_length bytes of Configuration
* ROM will be copied into that user space address. In either
* case, @rom_length is updated with the actual length of the
* configuration ROM.
* Configuration ROM.
* @rom: If non-zero, address of a buffer to be filled by a copy of the
* device's configuration ROM
* device's Configuration ROM
* @bus_reset: If non-zero, address of a buffer to be filled by a
* &struct fw_cdev_event_bus_reset with the current state
* of the bus. This does not cause a bus reset to happen.
* @bus_reset_closure: Value of &closure in this and subsequent bus reset events
* @card: The index of the card this device belongs to
*
* The %FW_CDEV_IOC_GET_INFO ioctl is usually the very first one which a client
* performs right after it opened a /dev/fw* file.
*
* As a side effect, reception of %FW_CDEV_EVENT_BUS_RESET events to be read(2)
* is started by this ioctl.
*/
@ -615,7 +604,7 @@ struct fw_cdev_initiate_bus_reset {
* @handle: Handle to the descriptor, written by the kernel
*
* Add a descriptor block and optionally a preceding immediate key to the local
* node's configuration ROM.
* node's Configuration ROM.
*
* The @key field specifies the upper 8 bits of the descriptor root directory
* pointer and the @data and @length fields specify the contents. The @key
@ -630,9 +619,9 @@ struct fw_cdev_initiate_bus_reset {
* If successful, the kernel adds the descriptor and writes back a @handle to
* the kernel-side object to be used for later removal of the descriptor block
* and immediate key. The kernel will also generate a bus reset to signal the
* change of the configuration ROM to other nodes.
* change of the Configuration ROM to other nodes.
*
* This ioctl affects the configuration ROMs of all local nodes.
* This ioctl affects the Configuration ROMs of all local nodes.
* The ioctl only succeeds on device files which represent a local node.
*/
struct fw_cdev_add_descriptor {
@ -644,13 +633,13 @@ struct fw_cdev_add_descriptor {
};
/**
* struct fw_cdev_remove_descriptor - Remove contents from the configuration ROM
* struct fw_cdev_remove_descriptor - Remove contents from the Configuration ROM
* @handle: Handle to the descriptor, as returned by the kernel when the
* descriptor was added
*
* Remove a descriptor block and accompanying immediate key from the local
* nodes' configuration ROMs. The kernel will also generate a bus reset to
* signal the change of the configuration ROM to other nodes.
* nodes' Configuration ROMs. The kernel will also generate a bus reset to
* signal the change of the Configuration ROM to other nodes.
*/
struct fw_cdev_remove_descriptor {
__u32 handle;
@ -866,13 +855,8 @@ struct fw_cdev_stop_iso {
* @local_time: system time, in microseconds since the Epoch
* @cycle_timer: Cycle Time register contents
*
* The %FW_CDEV_IOC_GET_CYCLE_TIMER ioctl reads the isochronous cycle timer
* and also the system clock (%CLOCK_REALTIME). This allows to express the
* receive time of an isochronous packet as a system time.
*
* @cycle_timer consists of 7 bits cycleSeconds, 13 bits cycleCount, and
* 12 bits cycleOffset, in host byte order. Cf. the Cycle Time register
* per IEEE 1394 or Isochronous Cycle Timer register per OHCI-1394.
* Same as %FW_CDEV_IOC_GET_CYCLE_TIMER2, but fixed to use %CLOCK_REALTIME
* and only with microseconds resolution.
*
* In version 1 and 2 of the ABI, this ioctl returned unreliable (non-
* monotonic) @cycle_timer values on certain controllers.
@ -889,10 +873,17 @@ struct fw_cdev_get_cycle_timer {
* @clk_id: input parameter, clock from which to get the system time
* @cycle_timer: Cycle Time register contents
*
* The %FW_CDEV_IOC_GET_CYCLE_TIMER2 works like
* %FW_CDEV_IOC_GET_CYCLE_TIMER but lets you choose a clock like with POSIX'
* clock_gettime function. Supported @clk_id values are POSIX' %CLOCK_REALTIME
* and %CLOCK_MONOTONIC and Linux' %CLOCK_MONOTONIC_RAW.
* The %FW_CDEV_IOC_GET_CYCLE_TIMER2 ioctl reads the isochronous cycle timer
* and also the system clock. This allows to correlate reception time of
* isochronous packets with system time.
*
* @clk_id lets you choose a clock like with POSIX' clock_gettime function.
* Supported @clk_id values are POSIX' %CLOCK_REALTIME and %CLOCK_MONOTONIC
* and Linux' %CLOCK_MONOTONIC_RAW.
*
* @cycle_timer consists of 7 bits cycleSeconds, 13 bits cycleCount, and
* 12 bits cycleOffset, in host byte order. Cf. the Cycle Time register
* per IEEE 1394 or Isochronous Cycle Timer register per OHCI-1394.
*/
struct fw_cdev_get_cycle_timer2 {
__s64 tv_sec;
@ -1014,4 +1005,6 @@ struct fw_cdev_receive_phy_packets {
__u64 closure;
};
#define FW_CDEV_VERSION 3 /* Meaningless legacy macro; don't use it. */
#endif /* _LINUX_FIREWIRE_CDEV_H */