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From: Arnd Bergmann <arnd@arndb.de>
To: Alexandre Courbot <acourbot@nvidia.com>
Cc: Linus Walleij <linus.walleij@linaro.org>, Thierry Reding <thierry.reding@gmail.com>, Sebastian Reichel <sre@kernel.org>, Wolfram Sang <wsa@the-dreams.de>, Jonathan Cameron <jic23@kernel.org>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, Alexander Shiyan <shc_work@mail.ru>, Hans Verkuil <hans.verkuil@cisco.com>, Mauro Carvalho Chehab <m.chehab@samsung.com>, Samuel Ortiz <sameo@linux.intel.com>, Lee Jones <lee.jones@linaro.org>, Chris Ball <chris@printf.net>, Ulf Hansson <ulf.hansson@linaro.org>, Florian Fainelli <f.fainelli@gmail.com>, Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>, David Woodhouse <dwmw2@infradead.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Jiri Slaby <jslaby@suse.cz>, Jingoo Han <jg1.han@samsung.com>, Bryan Wu <cooloney@gmail.com>, Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>, Tomi Valkeinen <tomi.valkeinen@ti.com>, Johannes Berg <johannes@sipsolutions.net>, "John W. Linville" <linville@tuxdriver.com>, "David S. Miller" <davem@dave
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 nurou@gmail.com
Subject: Re: [PATCH] gpio: extend gpiod_get*() with flags parameter
Date: Thu, 24 Jul 2014 18:10:30 +0200
Message-ID: <6059032.T3tqvLkWTo@wuerfel>
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References: <1406214298-20062-1-git-send-email-acourbot@nvidia.com>
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On Friday 25 July 2014 00:04:58 Alexandre Courbot wrote:
> I'm not sure how this could be applied harmlessly though - maybe through
> a dedicated branch for -next? Problem is that a lot of new code is not
> yet merged into mainline, and conflicts are very likely to occur. Linus,
> do you have any suggestion as to how this can be done without blood being
> spilled?

There is a trick that we sometime use in this situation,
though it has to be done carefully:
 
> diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
> index 7ff30d2..a3fb1d7 100644
> --- a/Documentation/gpio/consumer.txt
> +++ b/Documentation/gpio/consumer.txt
> @@ -29,13 +29,24 @@ gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the
>  device that will use the GPIO and the function the requested GPIO is supposed to
>  fulfill:
>  
> -       struct gpio_desc *gpiod_get(struct device *dev, const char *con_id)
> +       struct gpio_desc *gpiod_get(struct device *dev, const char *con_id,
> +                                   enum gpio_flags flags)
>  
> 


-	struct gpio_desc *gpiod_get(struct device *dev, const char *con_id)
+	struct gpio_desc *__gpiod_get(struct device *dev, const char *con_id,
+					enum gpio_flags flags);
+
+#define __gpiod_get(dev, con_id, flags, ...) __gpiod_get(dev, con_id, flags)
+#define gpiod_get(varargs ...) __gpiod_get(varargs, 0)

This will allow both variants to be called, and any users of the three-argument
version will pass zero as the fourth argument (or whatever you choose there).

Once the conversion is complete, the macros can be removed.

	ARnd