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

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Date:	Mon, 27 Oct 2014 16:30:34 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	RR <rajaram.officemails@...il.com>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	Muthu Mani <muth@...ress.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rajaram Regupathy <rera@...ress.com>,
	Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH v3 3/3] gpio: add support for Cypress CYUSBS234 USB-GPIO adapter

On Thu, Oct 9, 2014 at 1:46 AM, RR <rajaram.officemails@...il.com> wrote:
> On Wed, Oct 8, 2014 at 12:18 AM, Alexandre Courbot <gnurou@...il.com> wrote:
>> On Wed, Oct 8, 2014 at 4:09 PM, Muthu Mani <muth@...ress.com> wrote:

>>>> > +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
>> implementation?
>>
>>> 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.
>
> Does a driver targeted for a custom device has to implement every
> functionality in the 1st version ?

When you post a driver to the GPIO maintainers it is *NOT* tageted
at a consumer device, it is targeted at the kernel community and
upstream maintainers.

Of course you can deliver add-on patches out-of-tree to your
customers, it's generally a bad idea for the long term and maintenance
of your driver, but it's your pick.

Yours,
Linus Walleij
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