From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sylwester Nawrocki <snjw23@gmail.com>
Date: Fri, 13 Jan 2012 21:30:15 +0000
Subject: Re: [PATCH] video: s3c-fb: Add device tree support
Message-Id: <4F10A267.2020608@gmail.com>
List-Id: <linux-fbdev.vger.kernel.org>
References: <1326139307-25112-1-git-send-email-thomas.abraham@linaro.org>
 <4F109C04.5090600@gmail.com>
In-Reply-To: <4F109C04.5090600@gmail.com>
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To: linux-arm-kernel@lists.infradead.org

On 01/13/2012 10:03 PM, Sylwester Nawrocki wrote:
> On 01/09/2012 09:01 PM, Thomas Abraham wrote:
>>
>> +	for (idx = 0; idx<   nr_gpios; idx++) {
>> +		gpio = of_get_gpio(dev->of_node, idx);
>> +		if (!gpio_is_valid(gpio)) {
>> +			dev_err(dev, "invalid gpio[%d]: %d\n", idx, gpio);
>> +			return -EINVAL;
>> +		}
>> +
>> +		if (!request)
>> +			continue;
>> +
>> +		ret = gpio_request(gpio, "fimd");
> 
> Is it how it normally is supposed to be done, i.e. configuring a gpio
> _before_ it has been requested ? of_get_gpio() indirectly touches the
> gpio controller and gpio_request() doesn't seem to serve its purpose
> in this case, i.e. if there is situation like:
> 
> driver A                        driver B
> 
> of_get_gpio(nodeA, gpioA);
>                                  of_get_gpio(nodeB, gpioA);
> gpio_request(gpioA);
>                                  gpio_request(gpioB);
                                               s/B/A
> 
> driver B will end up with configuration of gpioA from nodeA, not from
> nodeB.
 
ugh, I put it wrong, it should instead read:

"driver A will end up with configuration of gpioA from nodeB, not from
nodeA."
 
> As there are few drivers doing that I must be missing something,
> not sure what..
> I realize the GPIO number needs to be known in order for a GPIO to be
> requested. Shouldn't of_get_gpio() be extended to allow locking gpio
> controller's module and marking a GPIO as requested in advance ?
> 
>> +		if (ret) {
>> +			dev_err(dev, "gpio [%d] request failed\n", gpio);
>> +			goto gpio_free;
>> +		}
>> +		sfb->gpios[idx] = gpio;
>> +	}
>> +	return 0;
>> +
>> +gpio_free:
>> +	while (--idx>= 0)
>> +		gpio_free(sfb->gpios[idx]);
>> +	return ret;
>> +}
>> +
>> +static void s3c_fb_dt_free_gpios(struct s3c_fb *sfb)
>> +{
>> +	unsigned int idx, nr_gpio;
>> +
>> +	nr_gpio = sfb->pdata->win[0]->max_bpp + 4;
>> +	for (idx = 0; idx<   nr_gpio; idx++)
>> +		gpio_free(sfb->gpios[idx]);
>> +}