[PATCH v5 12/12] can: slcan: extend the protocol with CAN state info

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

It extends the protocol to receive the adapter CAN state changes
(warning, busoff, etc.) and forward them to the netdev upper levels.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

---

(no changes since v4)

Changes in v4:
- Add description of slc_bump_state() function.
- Remove check for the 's' character at the beggining of the function.
  It was already checked by the caller function.
- Protect decoding against the case the frame len is longer than the
  received data (add SLC_STATE_FRAME_LEN macro).
- Set cf to NULL in case of alloc_can_err_skb() failure.
- Some small changes to make the decoding more readable.
- Use the character 'b' instead of 'f' for bus-off state.

Changes in v3:
- Drop the patch "can: slcan: simplify the device de-allocation".
- Add the patch "can: netlink: dump bitrate 0 if can_priv::bittiming.bitrate is -1U".

Changes in v2:
- Continue error handling even if no skb can be allocated.

 drivers/net/can/slcan/slcan-core.c | 74 +++++++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
index 4269b2267be2..54d29a410ad5 100644
--- a/drivers/net/can/slcan/slcan-core.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -78,7 +78,11 @@ MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
 #define SLC_CMD_LEN 1
 #define SLC_SFF_ID_LEN 3
 #define SLC_EFF_ID_LEN 8
-
+#define SLC_STATE_LEN 1
+#define SLC_STATE_BE_RXCNT_LEN 3
+#define SLC_STATE_BE_TXCNT_LEN 3
+#define SLC_STATE_FRAME_LEN       (1 + SLC_CMD_LEN + SLC_STATE_BE_RXCNT_LEN + \
+				   SLC_STATE_BE_TXCNT_LEN)
 struct slcan {
 	struct can_priv         can;
 	int			magic;
@@ -254,6 +258,72 @@ static void slc_bump_frame(struct slcan *sl)
 	dev_kfree_skb(skb);
 }
 
+/* A change state frame must contain state info and receive and transmit
+ * error counters.
+ *
+ * Examples:
+ *
+ * sb256256 : state bus-off: rx counter 256, tx counter 256
+ * sa057033 : state active, rx counter 57, tx counter 33
+ */
+static void slc_bump_state(struct slcan *sl)
+{
+	struct net_device *dev = sl->dev;
+	struct sk_buff *skb;
+	struct can_frame *cf;
+	char *cmd = sl->rbuff;
+	u32 rxerr, txerr;
+	enum can_state state, rx_state, tx_state;
+
+	switch (cmd[1]) {
+	case 'a':
+		state = CAN_STATE_ERROR_ACTIVE;
+		break;
+	case 'w':
+		state = CAN_STATE_ERROR_WARNING;
+		break;
+	case 'p':
+		state = CAN_STATE_ERROR_PASSIVE;
+		break;
+	case 'b':
+		state = CAN_STATE_BUS_OFF;
+		break;
+	default:
+		return;
+	}
+
+	if (state == sl->can.state || sl->rcount < SLC_STATE_FRAME_LEN)
+		return;
+
+	cmd += SLC_STATE_BE_RXCNT_LEN + SLC_CMD_LEN + 1;
+	cmd[SLC_STATE_BE_TXCNT_LEN] = 0;
+	if (kstrtou32(cmd, 10, &txerr))
+		return;
+
+	*cmd = 0;
+	cmd -= SLC_STATE_BE_RXCNT_LEN;
+	if (kstrtou32(cmd, 10, &rxerr))
+		return;
+
+	skb = alloc_can_err_skb(dev, &cf);
+	if (skb) {
+		cf->data[6] = txerr;
+		cf->data[7] = rxerr;
+	} else {
+		cf = NULL;
+	}
+
+	tx_state = txerr >= rxerr ? state : 0;
+	rx_state = txerr <= rxerr ? state : 0;
+	can_change_state(dev, cf, tx_state, rx_state);
+
+	if (state == CAN_STATE_BUS_OFF)
+		can_bus_off(dev);
+
+	if (skb)
+		netif_rx(skb);
+}
+
 /* An error frame can contain more than one type of error.
  *
  * Examples:
@@ -387,6 +457,8 @@ static void slc_bump(struct slcan *sl)
 		return slc_bump_frame(sl);
 	case 'e':
 		return slc_bump_err(sl);
+	case 's':
+		return slc_bump_state(sl);
 	default:
 		return;
 	}
-- 
2.32.0