From: Oliver Hartkopp <socketcan@hartkopp.net>
To: linux-can@vger.kernel.org
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Subject: [PATCH] can: isotp: support dynamic flow control parameters
Date: Fri,  8 Dec 2023 17:57:29 +0100
Message-Id: <20231208165729.3011-1-socketcan@hartkopp.net>
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The ISO15765-2 standard supports to take the PDUs communication parameters
blocksize (BS) and Separation Time minimum (STmin) either from the first
received flow control (FC) "static" or from every received FC "dynamic".

Add a new CAN_ISOTP_DYN_FC_PARMS flag to support dynamic FC parameters.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 include/uapi/linux/can/isotp.h | 1 +
 net/can/isotp.c                | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/can/isotp.h b/include/uapi/linux/can/isotp.h
index 439c982f7e81..6cde62371b6f 100644
--- a/include/uapi/linux/can/isotp.h
+++ b/include/uapi/linux/can/isotp.h
@@ -135,10 +135,11 @@ struct can_isotp_ll_options {
 #define CAN_ISOTP_FORCE_RXSTMIN	0x0100	/* ignore CFs depending on rx stmin */
 #define CAN_ISOTP_RX_EXT_ADDR	0x0200	/* different rx extended addressing */
 #define CAN_ISOTP_WAIT_TX_DONE	0x0400	/* wait for tx completion */
 #define CAN_ISOTP_SF_BROADCAST	0x0800	/* 1-to-N functional addressing */
 #define CAN_ISOTP_CF_BROADCAST	0x1000	/* 1-to-N transmission w/o FC */
+#define CAN_ISOTP_DYN_FC_PARMS	0x2000	/* dynamic FC parameters BS/STmin */
 
 /* protocol machine default values */
 
 #define CAN_ISOTP_DEFAULT_FLAGS		0
 #define CAN_ISOTP_DEFAULT_EXT_ADDRESS	0x00
diff --git a/net/can/isotp.c b/net/can/isotp.c
index d1c6f206f429..25bac0fafc83 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -379,12 +379,13 @@ static int isotp_rcv_fc(struct isotp_sock *so, struct canfd_frame *cf, int ae)
 		so->tx.state = ISOTP_IDLE;
 		wake_up_interruptible(&so->wait);
 		return 1;
 	}
 
-	/* get communication parameters only from the first FC frame */
-	if (so->tx.state == ISOTP_WAIT_FIRST_FC) {
+	/* get static/dynamic communication params from first/every FC frame */
+	if (so->tx.state == ISOTP_WAIT_FIRST_FC ||
+	    so->opt.flags & CAN_ISOTP_DYN_FC_PARMS) {
 		so->txfc.bs = cf->data[ae + 1];
 		so->txfc.stmin = cf->data[ae + 2];
 
 		/* fix wrong STmin values according spec */
 		if (so->txfc.stmin > 0x7F &&
-- 
2.39.2