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Subject[PATCH] 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>
---
applicable after patch
"firewire: cdev: prevent race between first get_info ioctl and bus reset event queuing"
Documentation/ABI/stable/firewire-cdev | 103 +++++++++++++++++++++++++
include/linux/firewire-cdev.h | 77 +++++++++----------
2 files changed, 138 insertions(+), 42 deletions(-)
Index: b/Documentation/ABI/stable/firewire-cdev
===================================================================
--- /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), epoll(2)
+ Watch for events to become available to be read.
+
+ read(2)
+ Receive various events. There are solicited events like
+ outbound asynchronous transaction completion, and unsolicited
+ events such as bus reset events, isochronous DMA buffer
+ completion, or PHY packet reception. Always use a read buffer
+ which is large enough to receive the largest event that could
+ ever arrive. See the documentation in <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, ...
Index: b/include/linux/firewire-cdev.h
===================================================================
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -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;
@@ -672,7 +661,7 @@ struct fw_cdev_remove_descriptor {
* @handle: Handle to context, written back by kernel
*
* Prior to sending or receiving isochronous I/O, a context must be created.
- * The context records information about the transmit or receive configuration
+ * The context records information about the transmit or receive Configuration
* and typically maps to an underlying hardware resource. A context is set up
* for either sending or receiving. It is bound to a specific isochronous
* @channel.
@@ -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 */

--
Stefan Richter
-=====-==-== -=== -=--=
http://arcgraph.de/sr/

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