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authorClemens Ladisch <clemens@ladisch.de>2010-03-31 16:26:52 +0200
committerStefan Richter <stefanr@s5r6.in-berlin.de>2010-04-10 16:51:13 +0200
commitaa6fec3cdeb14ecc916eb78c4cd9ed79e4f7fe8d (patch)
tree4beee35aa9f9e31ec542d11075b822de9adbacc6 /include
parent9cac00b8f0079d5d3d54ec4dae453d58dec30e7c (diff)
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/firewire-cdev.h39
1 files changed, 33 insertions, 6 deletions
diff --git a/include/linux/firewire-cdev.h b/include/linux/firewire-cdev.h
index 40b11013408..011fdf1eaec 100644
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -438,7 +438,7 @@ struct fw_cdev_remove_descriptor {
* @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 @@ struct fw_cdev_remove_descriptor {
* 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_create_iso_context {
*
* &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.
- *
- * FIXME - finish this documentation
+ * Use the FW_CDEV_ISO_ macros to fill in @control.
+ *
+ * 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 @@ struct fw_cdev_iso_packet {
* 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.
*