Option to ignore error frames

[yanick-douven]

Finalized implementation of #362 with the addition of:

• ROS parameter parsing (ignore-errors/error-name=true/false)
• CAN_ERR_LOSTARB is ignored by default
• tested on physical CAN bus

[Timple]

Since technically speaking the default behavior changes with this PR. Could this PR be evaluated before the official noetic release?

To prevent any discussions later if defaults can/might/should be changed within a release.

[mathias-luedtke]

Could this PR be evaluated before the official noetic release?

I had a brief look already. I cannot promise that I will have enough time until May 23.

My quick review:

• the default error mask should be kept as-is, perhaps configurable
• the handling of the errors should be configurable, arbitration lost error should get ignored
• serializable_map is not needed, can::Settings should be subclassed if you want to offer an API
• https://github.com/ros-industrial/ros_canopen/blob/162c0a8b20fda2f2a4b13ab1c26e1437beeacdb3/canopen_motor_node/src/motor_chain.cpp#L8 should be used for ROS, perhaps templated to not depend on XmlRpcValue directly
• canopen_chain_node should pass the settings to CANLayer somehow.

To prevent any discussions later if defaults can/might/should be changed within a release.

I don't want to branch off for noetic. Only the arbitration lost error should get handled differently. This change will affect melodic and noetic.

[yanick-douven]

@ipa-mdl Thank you for taking the time to review! Few comments/considerations:

• the default error mask should be kept as-is, perhaps configurable
• the handling of the errors should be configurable, arbitration lost error should get ignored

This means a possible high load from kernel to user space, as mentioned here. Why should the kernel still report all errors if we are ignoring them anyways in the user space?

• serializable_map is not needed, can::Settings should be subclassed if you want to offer an API

I will move (parts of) serializable_map into a subclassed version of can::Settings.

• https://github.com/ros-industrial/ros_canopen/blob/162c0a8b20fda2f2a4b13ab1c26e1437beeacdb3/canopen_motor_node/src/motor_chain.cpp#L8 should be used for ROS, perhaps templated to not depend on XmlRpcValue directly

After sending the settings to can::SocketCANInterface::init() we are leaving the ROS side of things, so what would we need XmlRpcSettings for? These ignored_errors-settings are generic and not ROS-specific.

• canopen_chain_node should pass the settings to CANLayer somehow.

I don't understand exactly what you mean, does this refer to the handling of errors?

This change will affect melodic and noetic.

Good to hear!

[mathias-luedtke]

superseded by https://github.com/ros-industrial/ros_canopen/pull/362