firewire: cdev: iso packet documentation

Add the missing documentation for iso packets. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

firewire: cdev: iso packet documentation
Add the missing documentation for iso packets. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Clemens Ladisch · Stefan Richter
1 parent 9cac00b8f0
Showing 1 changed file with 33 additions and 6 deletions Side-by-side Diff
include/linux/firewire-cdev.h
@@ -438,7 +438,7 @@
  * @type:	%FW_CDEV_ISO_CONTEXT_TRANSMIT or %FW_CDEV_ISO_CONTEXT_RECEIVE
  * @header_size: Header size to strip for receive contexts
  * @channel:	Channel to bind to
- * @speed:	Speed to transmit at
+ * @speed:	Speed for transmit contexts
  * @closure:	To be returned in &fw_cdev_event_iso_interrupt
  * @handle:	Handle to context, written back by kernel
  *
@@ -451,6 +451,9 @@
  * If a context was successfully created, the kernel writes back a handle to the
  * context, which must be passed in for subsequent operations on that context.
  *
+ * For receive contexts, @header_size must be at least 4 and must be a multiple
+ * of 4.
+ *
  * Note that the effect of a @header_size > 4 depends on
  * &fw_cdev_get_info.version, as documented at &fw_cdev_event_iso_interrupt.
  */
  
@@ -481,10 +484,34 @@
  *
  * &struct fw_cdev_iso_packet is used to describe isochronous packet queues.
  *
- * Use the FW_CDEV_ISO_ macros to fill in @control.  The sy and tag fields are
- * specified by IEEE 1394a and IEC 61883.
+ * Use the FW_CDEV_ISO_ macros to fill in @control.
  *
- * FIXME - finish this documentation
+ * For transmit packets, the header length must be a multiple of 4 and specifies
+ * the numbers of bytes in @header that will be prepended to the packet's
+ * payload; these bytes are copied into the kernel and will not be accessed
+ * after the ioctl has returned.  The sy and tag fields are copied to the iso
+ * packet header (these fields are specified by IEEE 1394a and IEC 61883-1).
+ * The skip flag specifies that no packet is to be sent in a frame; when using
+ * this, all other fields except the interrupt flag must be zero.
+ *
+ * For receive packets, the header length must be a multiple of the context's
+ * header size; if the header length is larger than the context's header size,
+ * multiple packets are queued for this entry.  The sy and tag fields are
+ * ignored.  If the sync flag is set, the context drops all packets until
+ * a packet with a matching sy field is received (the sync value to wait for is
+ * specified in the &fw_cdev_start_iso structure).  The payload length defines
+ * how many payload bytes can be received for one packet (in addition to payload
+ * quadlets that have been defined as headers and are stripped and returned in
+ * the &fw_cdev_event_iso_interrupt structure).  If more bytes are received, the
+ * additional bytes are dropped.  If less bytes are received, the remaining
+ * bytes in this part of the payload buffer will not be written to, not even by
+ * the next packet, i.e., packets received in consecutive frames will not
+ * necessarily be consecutive in memory.  If an entry has queued multiple
+ * packets, the payload length is divided equally among them.
+ *
+ * When a packet with the interrupt flag set has been completed, the
+ * &fw_cdev_event_iso_interrupt event will be sent.  An entry that has queued
+ * multiple receive packets is completed when its last packet is completed.
  */
 struct fw_cdev_iso_packet {
 	__u32 control;
@@ -501,7 +528,7 @@
  * Queue a number of isochronous packets for reception or transmission.
  * This ioctl takes a pointer to an array of &fw_cdev_iso_packet structs,
  * which describe how to transmit from or receive into a contiguous region
- * of a mmap()'ed payload buffer.  As part of the packet descriptors,
+ * of a mmap()'ed payload buffer.  As part of transmit packet descriptors,
  * a series of headers can be supplied, which will be prepended to the
  * payload during DMA.
  *
...	...	@@ -438,7 +438,7 @@
438	438	* @type: %FW_CDEV_ISO_CONTEXT_TRANSMIT or %FW_CDEV_ISO_CONTEXT_RECEIVE
439	439	* @header_size: Header size to strip for receive contexts
440	440	* @channel: Channel to bind to
441		- * @speed: Speed to transmit at
	441	+ * @speed: Speed for transmit contexts
442	442	* @closure: To be returned in &fw_cdev_event_iso_interrupt
443	443	* @handle: Handle to context, written back by kernel
444	444	*
...	...	@@ -451,6 +451,9 @@
451	451	* If a context was successfully created, the kernel writes back a handle to the
452	452	* context, which must be passed in for subsequent operations on that context.
453	453	*
	454	+ * For receive contexts, @header_size must be at least 4 and must be a multiple
	455	+ * of 4.
	456	+ *
454	457	* Note that the effect of a @header_size > 4 depends on
455	458	* &fw_cdev_get_info.version, as documented at &fw_cdev_event_iso_interrupt.
456	459	*/
457	460
...	...	@@ -481,10 +484,34 @@
481	484	*
482	485	* &struct fw_cdev_iso_packet is used to describe isochronous packet queues.
483	486	*
484		- * Use the FW_CDEV_ISO_ macros to fill in @control. The sy and tag fields are
485		- * specified by IEEE 1394a and IEC 61883.
	487	+ * Use the FW_CDEV_ISO_ macros to fill in @control.
486	488	*
487		- * FIXME - finish this documentation
	489	+ * For transmit packets, the header length must be a multiple of 4 and specifies
	490	+ * the numbers of bytes in @header that will be prepended to the packet's
	491	+ * payload; these bytes are copied into the kernel and will not be accessed
	492	+ * after the ioctl has returned. The sy and tag fields are copied to the iso
	493	+ * packet header (these fields are specified by IEEE 1394a and IEC 61883-1).
	494	+ * The skip flag specifies that no packet is to be sent in a frame; when using
	495	+ * this, all other fields except the interrupt flag must be zero.
	496	+ *
	497	+ * For receive packets, the header length must be a multiple of the context's
	498	+ * header size; if the header length is larger than the context's header size,
	499	+ * multiple packets are queued for this entry. The sy and tag fields are
	500	+ * ignored. If the sync flag is set, the context drops all packets until
	501	+ * a packet with a matching sy field is received (the sync value to wait for is
	502	+ * specified in the &fw_cdev_start_iso structure). The payload length defines
	503	+ * how many payload bytes can be received for one packet (in addition to payload
	504	+ * quadlets that have been defined as headers and are stripped and returned in
	505	+ * the &fw_cdev_event_iso_interrupt structure). If more bytes are received, the
	506	+ * additional bytes are dropped. If less bytes are received, the remaining
	507	+ * bytes in this part of the payload buffer will not be written to, not even by
	508	+ * the next packet, i.e., packets received in consecutive frames will not
	509	+ * necessarily be consecutive in memory. If an entry has queued multiple
	510	+ * packets, the payload length is divided equally among them.
	511	+ *
	512	+ * When a packet with the interrupt flag set has been completed, the
	513	+ * &fw_cdev_event_iso_interrupt event will be sent. An entry that has queued
	514	+ * multiple receive packets is completed when its last packet is completed.
488	515	*/
489	516	struct fw_cdev_iso_packet {
490	517	__u32 control;
...	...	@@ -501,7 +528,7 @@
501	528	* Queue a number of isochronous packets for reception or transmission.
502	529	* This ioctl takes a pointer to an array of &fw_cdev_iso_packet structs,
503	530	* which describe how to transmit from or receive into a contiguous region
504		- * of a mmap()'ed payload buffer. As part of the packet descriptors,
	531	+ * of a mmap()'ed payload buffer. As part of transmit packet descriptors,
505	532	* a series of headers can be supplied, which will be prepended to the
506	533	* payload during DMA.
507	534	*