Re: RFC: gpio: mmio: add support for 3 direction regs

From: Vladimir Zapolskiy
Date: Thu Jan 03 2019 - 03:07:22 EST

Hi Ramon,

On 01/03/2019 09:36 AM, Fried, Ramon wrote:
> Hi.
> I'm working on a driver for STA2X11 GPIO controller who seems to fit
> best to the generic mmio driver,

I hope you have seen the existing driver drivers/gpio/gpio-sta2x11.c

> the only problem I have is with the dir register case. The STA2X11
> has 3 registers for dir, one for data, one for set and one for
> clear. The generic-mmio driver has support for this fashion for the
> dat & set & clear registers but not for dirout/dirin registers.
> I wonder if support for this is generic enough to deserve a patch, if
> so I'm willing to quickly add this support, if not, adding a flag
> such as below, will allow partly using the generic mmio driver only
> for set/get and the direction can be handled outside the driver.

If gpio-mmio fits well, then it might be simpler to set a flag
BGPIOF_UNREADABLE_REG_DIR, then call bgpio_init() and then overwrite
.direction_input, .direction_output and .get_direction callbacks,
as a reference you can take a look at gpio-74xx-mmio.c

Best wishes,