linux-kernel - Re: [PATCH V2 7/7] USB: serial: f81232: Add gpiolib to GPIO device

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Date:   Thu, 9 Jan 2020 10:43:48 +0800
From:   "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, peter_hong@...tek.com.tw,
        "Ji-Ze Hong (Peter Hong)" <hpeter+linux_kernel@...il.com>
Subject: Re: [PATCH V2 7/7] USB: serial: f81232: Add gpiolib to GPIO device

Hi Johan,

Johan Hovold 於 2020/1/8 下午 10:46 寫道:
> On Wed, Oct 30, 2019 at 10:00:12AM +0800, Ji-Ze Hong (Peter Hong) wrote:

>> We had 2 type about GPIO pins, MODEx_y & GPIOxx. All MODEx_y & GPIOxx
>> are GPIOs and can be controlled by GPIO device, but they had some
>> difference about usage.
>> 	MODEx_y:
>> 		1. 3 pins(x: 0/1/2) can be access by UART port y.
>> 		2. Used to control UART's transceiver normally, but it
>> 		   also can be configure as GPIO when UART disabled by
>> 		   H/W (DTR strap to GND).
>> 	GPIOxx:
>> 		1. Access only by GPIO device.
>>
>> The series patch only support RS233 mode for all serial port, So we'll
>> direct set all MODEx_y to (0/0/1) for our demo board for default. If
>> user really want to use the pin, we had provide the gpiolib with GPIO
>> device, but we'll recommend user to use GPIOxy first.
> 
> Do you mean that you'd need to register a separate gpio chip per port in
> order to expose an interface for changing the MODEx_y pins for an
> enabled UART? Or can you do that through the "global" gpio device?

No, I still implement the gpiolib in GPIO Device. Sorry for bad
describe.

>> Is any suggest about this ? Could I maintain this for this series patch?
> 
> I understood from your other mail that the gpio device would not be able
> to control the pins of an enabled port. In either case, I think you need
> to refuse a request for a pin that's already in use by the corresponding
> port.

OK, I'll change the code as previous mail as following:

I can read the UART enable state from GPIO Device, so I can do when the
GPIO is associated with UART enabled, change it as output only otherwise
can be set to input/output.

> Also is there a way to determine the number of available pins by
> detecting the chip/package type? I'm assuming not all 36 pins are always
> accessible?

Yes, we had register to get package type, I'll add UART enable & package
type to determinate final GPIO pin out.

-- 
With Best Regards,
Peter Hong