[PATCH] Handle reg-shift property for of_serial ports

Segher Boessenkool segher at kernel.crashing.org
Sun Jul 8 08:12:09 EST 2007

>>> Given the existence of the boards, it looks correct to do this.
>>> However, I wonder if it was correct for the MV64660 to claim
>>> compatibily witn ns16550 if the programming model is not exactly
>>> the same. The official OF serial port bindings don't mention the
>>> reg-shift property, so it maybe would have been better to have
>    I'd preferred "reg-stride" or "reg-size" but see below...

It is not the register size.  "Register spacing" is the most
common name I believe, but "register shift" is nicer for
computer programs.

>>> a different value for the "compatible" property, in order not
>>> to confuse existing operating systems that implement the standard.
>> Ok, how about 'sparse16550'? Otherwise identical to ns16550, but with
>     Erm, wouldn't it be *too* generic approach?  I'd suggest to  
> name the
> device with its own name and make of_serial.c recognize it and  
> register with
> 8250.c as needed.

Yes, name the device by its real name, *please*.

>> the reg-shift property. I'll send a patch shortly, and I'll  
>> reorder the
>> match table -- if something claims compatibility with both 8250 and
>> 16550, shouldn't we drive it as the latter?
>     Certainly. BTW, was there really "ns8250" -- 8250 is Intel's chip?

It should be "i8250" yes.  Not that you'd ever find any anymore
of course.  And in many cases, it should be "pnpPNP,xxx" anyway.


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