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Subject[PATCH v4 12/12] can: slcan: extend the protocol with CAN state info
Date
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>

---

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 6c7c815eaf45..e2d7645ff8d2 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;
@@ -255,6 +259,72 @@ 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:
@@ -388,6 +458,8 @@ 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
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