canfd: remove redundant CAN FD flag

[pandora-kernel.git] / include / linux / can.h

diff --git a/include/linux/can.h b/include/linux/can.h
index 018055e..e52958d 100644 (file)
--- a/include/linux/can.h
+++ b/include/linux/can.h
@@ -74,20 +74,21 @@ struct can_frame {
 /*
  * defined bits for canfd_frame.flags
  *
- * As the default for CAN FD should be to support the high data rate in the
- * payload section of the frame (HDR) and to support up to 64 byte in the
- * data section (EDL) the bits are only set in the non-default case.
- * Btw. as long as there's no real implementation for CAN FD network driver
- * these bits are only preliminary.
+ * The use of struct canfd_frame implies the Extended Data Length (EDL) bit to
+ * be set in the CAN frame bitstream on the wire. The EDL bit switch turns
+ * the CAN controllers bitstream processor into the CAN FD mode which creates
+ * two new options within the CAN FD frame specification:
  *
- * RX: NOHDR/NOEDL - info about received CAN FD frame
- *     ESI         - bit from originating CAN controller
- * TX: NOHDR/NOEDL - control per-frame settings if supported by CAN controller
- *     ESI         - bit is set by local CAN controller
+ * Bit Rate Switch - to indicate a second bitrate is/was used for the payload
+ * Error State Indicator - represents the error state of the transmitting node
+ *
+ * As the CANFD_ESI bit is internally generated by the transmitting CAN
+ * controller only the CANFD_BRS bit is relevant for real CAN controllers when
+ * building a CAN FD frame for transmission. Setting the CANFD_ESI bit can make
+ * sense for virtual CAN interfaces to test applications with echoed frames.
  */
-#define CANFD_NOHDR 0x01 /* frame without high data rate */
-#define CANFD_NOEDL 0x02 /* frame without extended data length */
-#define CANFD_ESI   0x04 /* error state indicator */
+#define CANFD_BRS 0x01 /* bit rate switch (second bitrate for payload data) */
+#define CANFD_ESI 0x02 /* error state indicator of the transmitting node */
 
 /**
  * struct canfd_frame - CAN flexible data rate frame structure