Re: [PATCH v3 3/3] gpio: add support for Cypress CYUSBS234 USB-GPIO adapter

From: Alexandre Courbot
Date: Wed Oct 08 2014 - 03:19:01 EST

On Wed, Oct 8, 2014 at 4:09 PM, Muthu Mani <muth@xxxxxxxxxxx> wrote:
>> -----Original Message-----
>> From: Alexandre Courbot [mailto:gnurou@xxxxxxxxx]
>> Sent: Tuesday, October 07, 2014 3:34 PM
>> To: Muthu Mani
>> Cc: Samuel Ortiz; Lee Jones; Wolfram Sang; Linus Walleij; Greg Kroah-
>> Hartman; linux-i2c@xxxxxxxxxxxxxxx; linux-gpio@xxxxxxxxxxxxxxx; linux-
>> usb@xxxxxxxxxxxxxxx; Linux Kernel Mailing List; Rajaram Regupathy; Johan
>> Hovold
>> Subject: Re: [PATCH v3 3/3] gpio: add support for Cypress CYUSBS234 USB-
>> GPIO adapter
>> On Mon, Oct 6, 2014 at 11:47 PM, Muthu Mani <muth@xxxxxxxxxxx> wrote:
>> > +
>> > +static int cy_gpio_direction_input(struct gpio_chip *chip,
>> > + unsigned offset) {
>> > + return 0;
>> > +}
>> > +
>> > +static int cy_gpio_direction_output(struct gpio_chip *chip,
>> > + unsigned offset, int value) {
>> > + return 0;
>> > +}
>> If that chip is capable of both output and input, shouldn't these functions be
>> implemented? I think this has already been pointed out in a previous version
>> but you did not reply.
> Thanks for your inputs.
> Only the GPIOs which are configured to be output GPIO can be set.

In that case cy_gpio_set() should return an error for GPIOs which are
not configured as outputs. Is that guaranteed by the current

> The set operation would fail trying to set the input or unconfigured GPIOs.
> In this version of driver, this support is not added, it can be introduced in future versions.
> I will add a TODO note in the code.

Argh, no TODO please. Actual code that will turn this code into a
solid driver that can be merged.

Can all GPIOs be set as input or output? If so, please implement
cy_gpio_direction_*() and make sure that cy_gpio_set() behaves
properly if a GPIO is not an output. If the input/output GPIOs are
fixed, please make cy_gpio_direction_*() return an error if the GPIO
capabilities does not correspond to what is asked, and again ensure
that cy_gpio_set() works as expected.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at