Re: [PATCH 1/2] dt-binding: can: mcp2517fd: document device tree bindings

[kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org]

Hi Patrick!

> On 30.11.2017, at 17:44, Patrick Menschel <menschel.p-1KBjaw7Xf1+zQB+pC5nmwQ@public.gmane.org> wrote:
>> How would you try to present that HW-configuration in the 
>> device tree instead?
>> How would it impact the driver design?
>> 
> Hi,
> I'm afraid I don't know what is best practice but you may want to look
> at the max310x driver which declares it's GPIOs and GPIO based
> interrupts in the regular driver.
> 
> drivers/tty/serial/max310x.c
> Documentation/devicetree/bindings/serial/maxim,max310x.txt
> Look for "#ifdef CONFIG_GPIOLIB”.

This is a gpio-controller, for which this is what I would implement.

The problem comes more from the fact that the mcp2517fd is
primarily a CAN controller, which has a few GPIO pins.

So implementing a gpio-controller for those (rarely used) GPIOs
in the same driver seems a bit of an overkill.

The mcp2515 chip also supports 5 GPIO pins, but the driver
does not really make use of them, so they are left out.

The problem here is more the fact that the mcp2517fd supports
also push-pull/open-drain on some of those gpios.

And at least openDrain may be required on TXCan if used on a network
without a transceiver…

> My first try would be a single dt node like the max310x uses in the dt
> example.
> Imho it is better to make things useful before making them complicated.

The settings as they are now are the “simple” version.
implementing a separate GPIO-controller driver just to implement the same
logic we have now would make it a much bigger driver without lots of extra
benefits.

So I hope the current proposal is ok...

Martin--
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