diff options
Diffstat (limited to 'drivers/net/can/dev/length.c')
| -rw-r--r-- | drivers/net/can/dev/length.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/drivers/net/can/dev/length.c b/drivers/net/can/dev/length.c index 64673a8d1234..d35c4e82314d 100644 --- a/drivers/net/can/dev/length.c +++ b/drivers/net/can/dev/length.c @@ -38,3 +38,53 @@ u8 can_fd_len2dlc(u8 len) return len2dlc[len]; } EXPORT_SYMBOL_GPL(can_fd_len2dlc); + +/** + * can_skb_get_frame_len() - Calculate the CAN Frame length in bytes + * of a given skb. + * @skb: socket buffer of a CAN message. + * + * Do a rough calculation: bit stuffing is ignored and length in bits + * is rounded up to a length in bytes. + * + * Rationale: this function is to be used for the BQL functions + * (netdev_sent_queue() and netdev_completed_queue()) which expect a + * value in bytes. Just using skb->len is insufficient because it will + * return the constant value of CAN(FD)_MTU. Doing the bit stuffing + * calculation would be too expensive in term of computing resources + * for no noticeable gain. + * + * Remarks: The payload of CAN FD frames with BRS flag are sent at a + * different bitrate. Currently, the can-utils canbusload tool does + * not support CAN-FD yet and so we could not run any benchmark to + * measure the impact. There might be possible improvement here. + * + * Return: length in bytes. + */ +unsigned int can_skb_get_frame_len(const struct sk_buff *skb) +{ + const struct canfd_frame *cf = (const struct canfd_frame *)skb->data; + u8 len; + + if (can_is_canfd_skb(skb)) + len = canfd_sanitize_len(cf->len); + else if (cf->can_id & CAN_RTR_FLAG) + len = 0; + else + len = cf->len; + + if (can_is_canfd_skb(skb)) { + if (cf->can_id & CAN_EFF_FLAG) + len += CANFD_FRAME_OVERHEAD_EFF; + else + len += CANFD_FRAME_OVERHEAD_SFF; + } else { + if (cf->can_id & CAN_EFF_FLAG) + len += CAN_FRAME_OVERHEAD_EFF; + else + len += CAN_FRAME_OVERHEAD_SFF; + } + + return len; +} +EXPORT_SYMBOL_GPL(can_skb_get_frame_len); |