From mboxrd@z Thu Jan  1 00:00:00 1970
From: Timur Tabi <timur@codeaurora.org>
Subject: Re: [PATCH 1/2] [v5] pinctrl: qcom: disable GPIO groups with no pins
Date: Thu, 19 Oct 2017 17:44:59 -0500
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To: Linus Walleij <linus.walleij@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>, Andy Gross <andy.gross@linaro.org>, David Brown <david.brown@linaro.org>, anjiandi@codeaurora.org, "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>
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On 10/07/2017 06:07 AM, Linus Walleij wrote:
> I mean that you add
> unsigned long *line_valid_mask;
> to struct gpio_chip using the same type of logic
> as .irq_valid_mask. The mask should be optional.
> 
> Then the operation gpiod_get[_index]() will FAIL if the
> line is not valid.
> 
> There is no need to check on every operation, there should
> be no way to get a handle on the pin any other way.
> 
> All new code should be using descriptors at this point so we
> only need to design for that case.

I think I'm missing something, because I implemented what you're asking 
for, but whenever I try to expose a GPIO from sysfs (e.g. echo 37 > 
/sys/class/gpio/export), gpiod_get_index() is not called.  The only 
thing preventing the GPIO from being exported is the ->request callback:

static int msm_gpio_request(struct gpio_chip *chip, unsigned int offset)
{
	struct msm_pinctrl *pctrl = gpiochip_get_data(chip);
	const struct msm_pingroup *g = &pctrl->soc->groups[offset];

	if (!g->npins)
		return -ENODEV;

What operation is supposed to trigger a call to gpiod_get_index?

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