On 08/10/2017 05:05 AM, Sergei Shtylyov wrote:
> 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@xxxxxx>
>> ---
>> 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.
Ok
>
>> +
>> + 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.
Four lines up I am already setting max_bitrate to a default value of 0.
>
>> + 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
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
