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SubjectRe: [PATCH 1/4] can: dev: Add support for limiting configured bitrate
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Hello!

On 7/20/2017 2:36 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 fixed-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>
> ---
> drivers/net/can/dev.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/can/dev.h | 5 +++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
> index 365a8cc..fbab87d 100644
> --- a/drivers/net/can/dev.c
> +++ b/drivers/net/can/dev.c
[...]
> @@ -814,6 +830,38 @@ int open_candev(struct net_device *dev)
> }
> EXPORT_SYMBOL_GPL(open_candev);
>
> +#ifdef CONFIG_OF
> +void of_transceiver_is_fixed(struct net_device *dev)

Strange name for a *void* function...
Also, I think 'struct net_device *' variables are typically called 'ndev'.

> +{
> + struct device_node *dn;
> + struct can_priv *priv = netdev_priv(dev);
> + u32 max_frequency;
> + struct device_node *np;
> +
> + np = dev->dev.parent->of_node;
> +
> + /* New binding */
> + dn = of_get_child_by_name(np, "fixed-transceiver");
> + if (!dn)
> + return;
> +
> + of_property_read_u32(dn, "max-arbitration-speed", &max_frequency);

In case this function fails, 'max_frequency' will have no value -- you'd
better initialize it...

> +
> + if (max_frequency > 0)
> + priv->max_trans_arbitration_speed = max_frequency;
> + else
> + priv->max_trans_arbitration_speed = -1;
> +
> + of_property_read_u32(dn, "max-data-speed", &max_frequency);

Again, when that function fails, the variable will keep the value from the
previous call...

[...]

MBR, Sergei

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