From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: [alsa-devel] [PATCH 2/4] ASoC: s3c64xx/smartq: use dynamic registration
Date: Thu, 17 Jul 2014 12:58:25 +0200
Message-ID: <53C7AC51.6060200@metafoo.de>
References: <CAAVeFuJRCwSwcEOng2M6s+mWhJT8sUtsh7YGE-hBTGUFWAhtrQ@mail.gmail.com> <CAAVeFuLfgG6W1qK2ATTbq_ydEOjUuM8Wvftm6N1RK3Kz_y1zHg@mail.gmail.com> <20140716071237.GA7978@ulmo> <CAAVeFuJEjMBX+7vsLk5zXV5Moy=WDmWidpVZjQ_=8VD45+QdHg@mail.gmail.com> <20140716075107.GG7978@ulmo> <53C63CBA.20809@codethink.co.uk> <CAAVeFuK55XzwaU+eOWhfUxJ7wEwGqxRCPDZKf+gVeMgeV8ys6g@mail.gmail.com> <20140717074444.GB18640@ulmo> <CAAVeFuJQUA+92jGpgDkyQ+=Qu+okBHzS5aFi7gmdwh+qcFp3fg@mail.gmail.com> <20140717101723.GR17528@sirena.org.uk> <20140717104121.GF17877@ulmo>
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To: Thierry Reding <thierry.reding@gmail.com>, Mark Brown <broonie@kernel.org>
Cc: Alexandre Courbot <gnurou@gmail.com>, "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>, Rojhalat Ibrahim <imr@rtschenk.de>, Arnd Bergmann <arnd@arndb.de>, Tomasz Figa <t.figa@samsung.com>, Maurus Cuelenaere <mcuelenaere@gmail.com>, Liam Girdwood <lgirdwood@gmail.com>, "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>, Kukjin Kim <kgene.kim@samsung.com>, Rob Jones <rob.jones@codethink.co.uk>, Linus Walleij <linus.walleij@linaro.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>

On 07/17/2014 12:41 PM, Thierry Reding wrote:
> On Thu, Jul 17, 2014 at 11:17:23AM +0100, Mark Brown wrote:
>> On Thu, Jul 17, 2014 at 05:55:36PM +0900, Alexandre Courbot wrote:
>>
>>> Right. It may very well be that a single flag specifier (as opposed to
>>> an array) will be enough for this case. If you need to request some
>>> GPIOs as input and some other as output then they are clearly
>>> different functions and requesting them together would be an abuse of
>>> the API.
>>
>> Not so sure about that - what about requesting GPIOs for a bidirectional
>> bus?  Thinking about SPI bitbanging here.
>
> Wouldn't you want to use a different means that the gpiod_array_*() API
> to handle those cases? gpiod_array_*() is probably most useful to handle
> bulk operations on a set of GPIOs that do essentially the same thing. If
> you get and then need to index into that array to handle them all
> differently then you don't gain very much.

I think the goal of a gpiod_array_* API should be to make requesting 
multiple GPIOs that are used by a driver as convenient as possible and at 
the same time reduce the amount of boiler plate code necessary. E.g compare

gpios[0] = gpio_get(...);
if (IS_ERR(gpios[0])) {
	ret = PTR_ERR(gpios[0]);
	goto cleanup;
}

gpios[1] = gpio_get(...);
if (IS_ERR(gpios[1])) {
	ret = PTR_ERR(gpios[1]);
	goto cleanup;
}

gpios[2] = gpio_get(...);
if (IS_ERR(gpios[2])) {
	ret = PTR_ERR(gpioss[2]);
	goto cleanup;
}

with

ret = gpio_array_get(..., gpios);
if (ret)
	goto err_cleanup;

- Lars