Re: [PATCH] gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled
From: Uwe Kleine-König
Date: Fri Feb 20 2015 - 13:54:12 EST
On Thu, Feb 19, 2015 at 09:33:44PM -0800, Dmitry Torokhov wrote:
> On Fri, Feb 20, 2015 at 01:59:43PM +0900, Alexandre Courbot wrote:
> > On Fri, Feb 20, 2015 at 9:30 AM, Dmitry Torokhov
> > <dmitry.torokhov@xxxxxxxxx> wrote:
> > > Given the intent behind gpiod_get_optional() and friends it does not make
> > > sense to return -ENOSYS when GPIOLIB is disabled: the driver is expected to
> > > work just fine without gpio so let's behave as if gpio was not found.
> > > Otherwise we have to special-case -ENOSYS in drivers.
> > Interestingly Uwe sent a RFC for this one week ago:
> > http://patchwork.ozlabs.org/patch/439135/
> > Maybe credit him with a Suggested-by.?
> I certainly am fine with crediting him with Suggested-by even though I did not
> see that Uwe's e-mail but this patch was prompted by his other patch changing a
> few input drivers to use gpiod_get_optional() and me recalling that I
> explicitly did not use it as it made no difference from gpiod_get() since I had
> to handle -ENOSYS anyway.
Note that I'm not convinced any more this is a good idea. Consider you
have a device tree entry specifying
reset-gpio = <&gpio5 4 0>;
for your device.
gpiod_get_optional(dev, "reset", GPIO_OUT_LOW);
the drivers tells that some of the devices it can handle have a reset
gpio. If the device in question does have such a gpio the driver must
know and do something with it. If the device doesn't have such a gpio
that's fine, too.
But if GPIOLIB is off and the device has a reset-gpio specified you
certainly want to error out, right?
So IMHO the right thing to do is to return NULL iff there is no
reset-gpio specified. Otherwise -ENOSYS is the right thing to return.
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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