linux-kernel - Re: [PATCH v2] gpiolib: Export gpiochip_request_own_desc and gpiochip_free_own

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Date:	Tue, 22 Jul 2014 09:59:41 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH v2] gpiolib: Export gpiochip_request_own_desc and
 gpiochip_free_own_desc

On Mon, Jul 21, 2014 at 11:53:27PM -0700, Guenter Roeck wrote:
> On 07/21/2014 11:43 PM, Mika Westerberg wrote:
> >On Mon, Jul 21, 2014 at 10:18:25PM -0700, Guenter Roeck wrote:
> >>Both functions were introduced to let gpio drivers request their own
> >>gpio pins. Without exporting the functions, this can however only be
> >>used by gpio drivers built into the kernel.
> >
> >The reason why these are private to drivers is that those are dangerous
> >if used blindly.
> >
> >>Secondary impact is that the functions can not currently be used by
> >>platform initialization code associated with the gpio-pca953x driver.
> >>This code permits auto-export of gpio pins through platform data, but
> >>if this functionality is used, the module can no longer be unloaded due
> >>to the problem solved with the introduction of gpiochip_request_own_desc
> >>and gpiochip_free_own_desc.
> >>
> >>Export both function so they can be used from modules and from
> >>platform initialization code.
> >
> >However, you have valid reason above. I wonder if this requires
> >some documentation in Documentation/gpio/driver.txt?
> >
> Sure. Any idea what I should write, or do you want me to come up with something ?

Come up with something that lists valid usage of these two functions :)

Mainly that they are supposed to be used by GPIO chip drivers to request
their own GPIOs, not consumer drivers etc. And even in GPIO chip drivers
they should be used sparingly.

> 
> >>Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>
> >>Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> >>---
> >>v2: Move function declarations from consumer.h to driver.h.
> >>
> >>  drivers/gpio/gpiolib.c      | 2 ++
> >>  drivers/gpio/gpiolib.h      | 3 ---
> >>  include/linux/gpio/driver.h | 3 +++
> >>  3 files changed, 5 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> >>index 43d9e34..04c647e 100644
> >>--- a/drivers/gpio/gpiolib.c
> >>+++ b/drivers/gpio/gpiolib.c
> >>@@ -1953,6 +1953,7 @@ int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label)
> >>
> >>  	return __gpiod_request(desc, label);
> >>  }
> >>+EXPORT_SYMBOL(gpiochip_request_own_desc);
> >
> >EXPORT_SYMBOL_GPL?
> >
> Ok.
> 
> Thanks,
> Guenter
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