linux-kernel - Re: RFC: gpio: mmio: add support for 3 direction regs

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Date:   Thu, 3 Jan 2019 10:51:02 +0200
From:   "Fried, Ramon" <ramon.fried@...ux.intel.com>
To:     Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        linus.walleij@...aro.org, bgolaszewski@...libre.com,
        linux-gpio@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, vladimir.kondratiev@...ux.intel.com
Subject: Re: RFC: gpio: mmio: add support for 3 direction regs


On 1/3/2019 10:07, Vladimir Zapolskiy wrote:
> 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
I surely did. we have the same IP in our soc but it was changed a lot internally, don't want to litter the original.
>
>> 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

Nice.
That's an option I didn't think of, better than setting the flag. what about adding the generic support ?

>
> --
> Best wishes,
> Vladimir