Re: serial_ns16550 driver question

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, Jul 20, 2011 at 11:51:04PM +0400, Antony Pavlov wrote:
> Hi!
> 
> In include/ns16550.h we have:
> 
> struct NS16550_plat {
>         unsigned int clock;
>         unsigned char f_caps;
>         /**
>          * register read access capability
>          */
>         unsigned int (*reg_read) (unsigned long base, unsigned char reg_offset);
>         /**
>          * register write access capability
>          */
>         void (*reg_write) (unsigned int val, unsigned long base,
>                                     unsigned char reg_offset);
> };
> 
> Why reg_read and reg_write's argument base has type unsigned long?
> IMHO pointer type (void * or char *)  is more natural.

You're right, I also wondered about this recently when looking at a
patch on the list. I would also rather see void __iomem *. The problem
is that this driver is also used on X86 which uses inb/outb which take
an integer argument.
The Linux driver works around this by having a membase and a iobase
field along with different register accessors. While being cleaner
I'm unsure if we want to go this way.

Ssascha

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