Drop fake bittimings in favor of bitrate table

The fake bittiming table produces wrong results in Linux 4.19's bitrate
based parameter calculation.

SocketCAN support for fixed bitrates was introduced in 431af779256c in
Jan 2017, and as of Linux 4.18 the only driver using it is mcba_usb.
Bitrates are also fixed in ELM327, and none of the other parameters can
be tuned, so using this API makes sense here as well.

diff --git a/module/elmcan.c b/module/elmcan.c
index c3acc07f70f5da8cb1880e86ea8eeba09827742a..d5c289c82bc4c3b603115aca13592407cb420f89 100644 (file)
--- a/module/elmcan.c
+++ b/module/elmcan.c
@@ -1037,19 +1037,30 @@ static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
 
 
 
-/* Some fake bit timings to allow bitrate setting */
-static const struct can_bittiming_const elmcan_bittiming_const = {
-       .name = "elmcan",
-       .tseg1_min = 1,
-       .tseg1_max = 1,
-       .tseg2_min = 0,
-       .tseg2_max = 0,
-       .sjw_max = 1,
-       .brp_min = 1,
-       .brp_max = 500,
-       .brp_inc = 1,
+/* ELM327 can only handle bitrates that are integer divisors of 500 kHz,
+ * or 7/8 of that. Divisors are 1 to 64.
+ * Currently we don't implement support for 7/8 rates.
+ */
+static const u32 elmcan_bitrate_const[64] = {
+       7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
+       8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
+       10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
+       12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
+       15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
+       20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
+       31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
+       62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
 };
 
+/* Dummy function to claim we're changing the bitrate.
+ * We actually do this when opening the net device.
+ */
+static int elmcan_do_set_bittiming(struct net_device *netdev)
+{
+       return 0;
+}
+
+
 /*
  * Open the high-level part of the elmcan channel.
  * This function is called by the TTY module when the
@@ -1085,8 +1096,9 @@ static int elmcan_ldisc_open(struct tty_struct *tty)
 
        /* Configure CAN metadata */
        elm->can.state = CAN_STATE_STOPPED;
-       elm->can.clock.freq = 1000000;
-       elm->can.bittiming_const = &elmcan_bittiming_const;
+       elm->can.bitrate_const = elmcan_bitrate_const;
+       elm->can.bitrate_const_cnt = ARRAY_SIZE(elmcan_bitrate_const);
+       elm->can.do_set_bittiming = elmcan_do_set_bittiming;
        elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
 
        /* Configure netlink interface */