Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate
From: Sergei Shtylyov <hidden>
Date: 2017-08-10 10:05:19
Also in:
linux-can, lkml, netdev
Hello! On 8/10/2017 3:59 AM, Franklin S Cooper Jr wrote:
quoted hunk ↗ jump to hunk
Various CAN or CAN-FD IP may be able to run at a faster rate than what the transceiver the CAN node is connected to. This can lead to unexpected errors. However, CAN transceivers typically have fixed limitations and provide no means to discover these limitations at runtime. Therefore, add support for a can-transceiver node that can be reused by other CAN peripheral drivers to determine for both CAN and CAN-FD what the max bitrate that can be used. If the user tries to configure CAN to pass these maximum bitrates it will throw an error. Signed-off-by: Franklin S Cooper Jr <redacted> --- Version 4 changes: Used can-transceiver instead of fixed-transceiver. drivers/net/can/dev.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/can/dev.h | 5 +++++ 2 files changed, 55 insertions(+)diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 365a8cc..372108f 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c
[...]
quoted hunk ↗ jump to hunk
@@ -814,6 +815,39 @@ int open_candev(struct net_device *dev) } EXPORT_SYMBOL_GPL(open_candev); +#ifdef CONFIG_OF +/* + * Common function that can be used to understand the limitation of + * a transceiver when it provides no means to determine these limitations + * at runtime. + */ +void of_can_transceiver(struct net_device *dev) +{ + struct device_node *dn; + struct can_priv *priv = netdev_priv(dev); + struct device_node *np; + unsigned int max_bitrate; + int ret; + + np = dev->dev.parent->of_node;
I'd do that as an initializer.
+ + dn = of_get_child_by_name(np, "can-transceiver"); + if (!dn) + return; + + max_bitrate = 0; + ret = of_property_read_u32(dn, "max-bitrate", &max_bitrate);
I'd initialize max_bitrate to 0 as iff of_property_read_u32() fails, it'll
leave the variable unset...
+
+ if (max_bitrate > 0) {
You risk checking unset variable here.
+ priv->max_bitrate = max_bitrate;
+ priv->is_bitrate_limited = true;
+ } else if (ret != -EINVAL) {
+ netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
+ }
+}
+EXPORT_SYMBOL(of_can_transceiver);
+#endif
+
/*
* Common close function for cleanup before the device gets closed.
*[...] MBR, Sergei