diff options
| -rw-r--r-- | include/linux/firewire-cdev.h | 39 |
1 files changed, 33 insertions, 6 deletions
diff --git a/include/linux/firewire-cdev.h b/include/linux/firewire-cdev.h index 40b11013408e..011fdf1eaec5 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. * |