Merge patch series "can: esd_usb: Some more preparation for supporting esd CAN-USB/3"

Frank Jungclaus <frank.jungclaus@esd.eu> says:

Another small batch of patches to be seen as preparation for adding
support of the newly available esd CAN-USB/3 to esd_usb.c.

Due to some unresolved questions adding support for
CAN_CTRLMODE_BERR_REPORTING has been postponed to one of the future
patches.

v2 -> v3:
 * More specific subjects
 * Try to use imperative instead of past tense

v1 -> v2: https://lore.kernel.org/all/20230214160223.1199464-1-frank.jungclaus@esd.eu
 * [Patch v2 1/3]: No changes.
 * [Patch v2 2/3]: Make use of can_change_state() and relocate testing
   alloc_can_err_skb() for NULL to the end of esd_usb_rx_event(), to
   have things like can_bus_off(), can_change_state() working even in
   out of memory conditions.
 * [Patch v2 3/3]: No changes. I will 'declare esd_usb_msg as an union
   instead of a struct' in a separate follow-up patch.

v1: https://lore.kernel.org/all/20221219212013.1294820-1-frank.jungclaus@esd.eu
    https://lore.kernel.org/all/20221219212717.1298282-1-frank.jungclaus@esd.eu

Link: https://lore.kernel.org/all/20230216190450.3901254-1-frank.jungclaus@esd.euSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/esd_usb.c

@@ -127,7 +127,15 @@ struct rx_msg {
 	u8 dlc;
 	__le32 ts;
 	__le32 id; /* upper 3 bits contain flags */
-	u8 data[8];
+	union {
+		u8 data[8];
+		struct {
+			u8 status; /* CAN Controller Status */
+			u8 ecc;    /* Error Capture Register */
+			u8 rec;    /* RX Error Counter */
+			u8 tec;    /* TX Error Counter */
+		} ev_can_err_ext;  /* For ESD_EV_CAN_ERROR_EXT */
+	};
 };
 
 struct tx_msg {
@@ -229,51 +237,52 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
 	u32 id = le32_to_cpu(msg->msg.rx.id) & ESD_IDMASK;
 
 	if (id == ESD_EV_CAN_ERROR_EXT) {
-		u8 state = msg->msg.rx.data[0];
-		u8 ecc = msg->msg.rx.data[1];
-		u8 rxerr = msg->msg.rx.data[2];
-		u8 txerr = msg->msg.rx.data[3];
+		u8 state = msg->msg.rx.ev_can_err_ext.status;
+		u8 ecc = msg->msg.rx.ev_can_err_ext.ecc;
+		u8 rxerr = msg->msg.rx.ev_can_err_ext.rec;
+		u8 txerr = msg->msg.rx.ev_can_err_ext.tec;
 
 		netdev_dbg(priv->netdev,
 			   "CAN_ERR_EV_EXT: dlc=%#02x state=%02x ecc=%02x rec=%02x tec=%02x\n",
 			   msg->msg.rx.dlc, state, ecc, rxerr, txerr);
 
 		skb = alloc_can_err_skb(priv->netdev, &cf);
-		if (skb == NULL) {
-			stats->rx_dropped++;
-			return;
-		}
 
 		if (state != priv->old_state) {
+			enum can_state tx_state, rx_state;
+			enum can_state new_state = CAN_STATE_ERROR_ACTIVE;
+
 			priv->old_state = state;
 
 			switch (state & ESD_BUSSTATE_MASK) {
 			case ESD_BUSSTATE_BUSOFF:
-				priv->can.state = CAN_STATE_BUS_OFF;
-				cf->can_id |= CAN_ERR_BUSOFF;
-				priv->can.can_stats.bus_off++;
+				new_state = CAN_STATE_BUS_OFF;
 				can_bus_off(priv->netdev);
 				break;
 			case ESD_BUSSTATE_WARN:
-				priv->can.state = CAN_STATE_ERROR_WARNING;
-				priv->can.can_stats.error_warning++;
+				new_state = CAN_STATE_ERROR_WARNING;
 				break;
 			case ESD_BUSSTATE_ERRPASSIVE:
-				priv->can.state = CAN_STATE_ERROR_PASSIVE;
-				priv->can.can_stats.error_passive++;
+				new_state = CAN_STATE_ERROR_PASSIVE;
 				break;
 			default:
-				priv->can.state = CAN_STATE_ERROR_ACTIVE;
+				new_state = CAN_STATE_ERROR_ACTIVE;
 				txerr = 0;
 				rxerr = 0;
 				break;
 			}
-		} else {
+
+			if (new_state != priv->can.state) {
+				tx_state = (txerr >= rxerr) ? new_state : 0;
+				rx_state = (txerr <= rxerr) ? new_state : 0;
+				can_change_state(priv->netdev, cf,
+						 tx_state, rx_state);
+			}
+		} else if (skb) {
 			priv->can.can_stats.bus_error++;
 			stats->rx_errors++;
 
-			cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR |
-				      CAN_ERR_CNT;
+			cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
 
 			switch (ecc & SJA1000_ECC_MASK) {
 			case SJA1000_ECC_BIT:
@@ -286,7 +295,6 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
 				cf->data[2] |= CAN_ERR_PROT_STUFF;
 				break;
 			default:
-				cf->data[3] = ecc & SJA1000_ECC_SEG;
 				break;
 			}
 
@@ -294,20 +302,22 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
 			if (!(ecc & SJA1000_ECC_DIR))
 				cf->data[2] |= CAN_ERR_PROT_TX;
 
-			if (priv->can.state == CAN_STATE_ERROR_WARNING ||
-			    priv->can.state == CAN_STATE_ERROR_PASSIVE) {
-				cf->data[1] = (txerr > rxerr) ?
-					CAN_ERR_CRTL_TX_PASSIVE :
-					CAN_ERR_CRTL_RX_PASSIVE;
-			}
-			cf->data[6] = txerr;
-			cf->data[7] = rxerr;
+			/* Bit stream position in CAN frame as the error was detected */
+			cf->data[3] = ecc & SJA1000_ECC_SEG;
 		}
 
 		priv->bec.txerr = txerr;
 		priv->bec.rxerr = rxerr;
 
-		netif_rx(skb);
+		if (skb) {
+			cf->can_id |= CAN_ERR_CNT;
+			cf->data[6] = txerr;
+			cf->data[7] = rxerr;
+
+			netif_rx(skb);
+		} else {
+			stats->rx_dropped++;
+		}
 	}
 }