cpu/samd5x write can driver

[firas-hamdi]

Contribution description

This PR provides the samd5x CPU definition with the CAN controller driver.
The driver supports the initialization of the CAN controller, the send/receive operations set/remove filters and the test mode that sets the CAN controller in loop back (listens to the bus as well as the own transmitted messages)

Testing procedure

The PR provides also an application to test the driver using the same54-xpro board.
The CAN controller should receive only the messages having a CAN ID matching the filters.
The bus can be monitored using a PCAN-USB adapter or a logic analyser.

[benpicco]

Just some initial comments. I think you should just use the definitions from the vendor files when possible instead of re-defining them yourself.

[wosym]

It's been ages since I worked with CAN and RIOT also has changed quite a bit since I last used it, so I probably won't be able to add much.

One question I did have after skimming through the code is: what's up with the separate candev test? The original test (now found in tests/drivers/candev) was meant to be entirely agnostic to the device used. Just specify the CAN device you're using, flash to target, et voila! It works and does the same as it would on another device. This way, it's possible to have several different MCU's with different CAN devices all running the same example while still being able to communicate with each other. I wonder what the reason is for creating a separate test that appears to be doing more or less the same. I would suggest editing the existing test with some preprocessor code to select your same5 driver and change as little as possible aside from that.

[benpicco]

Why are the defaults only set that way for same54-xpro?
There can be other boards with that CAN peripheral

[firas-hamdi]

I saw in boards definition that it's the only board using the SAMD/E5x cpu, so I limited these defaults to this board. But you're right, I can leave that out

[firas-hamdi]

@benpicco I added a new variable here to leave these compilation flags just for the SAME54 family (as the only supporting CAN controllers)

[firas-hamdi]

I will make a commits cleanup after the next round of reviewing

[kfessel]

please squash your last 4 commits where they belong and put

add CAN RX mailbox feature

some where before them (the commit title needs area of work)

other than that this is good to go

if you like to you may rebase on master ( not required

[kfessel]

looks good 🎉

[kfessel]

🎉