Messages in this thread | | | Subject | Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate | From | Sergei Shtylyov <> | Date | Thu, 10 Aug 2017 13:05:14 +0300 |
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Hello!
On 8/10/2017 3:59 AM, Franklin S Cooper Jr wrote:
> 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 <fcooper@ti.com> > --- > 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 [...] > @@ -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
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