Re: [PATCH 1/4] can: dev: Add support for limiting configured bitrate
From: Sergei Shtylyov <hidden>
Date: 2017-07-20 09:52:20
Also in:
linux-can, linux-devicetree, lkml
Hello! On 7/20/2017 2:36 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 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 <redacted> --- 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
[...]
quoted hunk ↗ jump to hunk
@@ -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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