firewire: prevent dropping of completed iso packet header data

The buffer for the header data of completed iso packets has a fixed
size, so it is possible to configure a stream with a big interval
between interrupt packets or with big headers so that this buffer would
overflow.  Previously, ohci.c would drop any data that would not fit,
but this could make unsuspecting applications believe that fewer than
the actual number of packets have completed.

Instead of dropping data, add calls to flush_iso_completion() so that
there are as many events as needed to report all of the data.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/firewire-cdev.h b/include/linux/firewire-cdev.h
index cc1b570a2eb3..b9bd349c6930 100644
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -207,12 +207,15 @@ struct fw_cdev_event_request2 {
  * @closure:    See &fw_cdev_event_common;
  *              set by %FW_CDEV_CREATE_ISO_CONTEXT ioctl
  * @type:       See &fw_cdev_event_common; always %FW_CDEV_EVENT_ISO_INTERRUPT
- * @cycle:      Cycle counter of the interrupt packet
+ * @cycle:      Cycle counter of the last completed packet
  * @header_length: Total length of following headers, in bytes
  * @header:     Stripped headers, if any
  *
  * This event is sent when the controller has completed an &fw_cdev_iso_packet
- * with the %FW_CDEV_ISO_INTERRUPT bit set.
+ * with the %FW_CDEV_ISO_INTERRUPT bit set, or when there have been so many
+ * completed packets without the interrupt bit set that the kernel's internal
+ * buffer for @header is about to overflow.  (In the latter case, kernels with
+ * ABI version < 5 drop header data up to the next interrupt packet.)
  *
  * Isochronous transmit events (context type %FW_CDEV_ISO_CONTEXT_TRANSMIT):
  *
@@ -440,6 +443,8 @@ union fw_cdev_event {
  *               - added %FW_CDEV_EVENT_ISO_INTERRUPT_MULTICHANNEL,
  *                 %FW_CDEV_ISO_CONTEXT_RECEIVE_MULTICHANNEL, and
  *                 %FW_CDEV_IOC_SET_ISO_CHANNELS
+ *  5  (3.4)     - send %FW_CDEV_EVENT_ISO_INTERRUPT events when needed to
+ *                 avoid dropping data
  */
 
 /**