From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752871AbbBTFdv (ORCPT ); Fri, 20 Feb 2015 00:33:51 -0500 Received: from mail-pa0-f51.google.com ([209.85.220.51]:42294 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751354AbbBTFdt (ORCPT ); Fri, 20 Feb 2015 00:33:49 -0500 Date: Thu, 19 Feb 2015 21:33:44 -0800 From: Dmitry Torokhov To: Alexandre Courbot Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Linus Walleij , "linux-gpio@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH] gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled Message-ID: <20150220053344.GA5518@dtor-glaptop> References: <20150220003035.GA22334@dtor-glaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 20, 2015 at 01:59:43PM +0900, Alexandre Courbot wrote: > On Fri, Feb 20, 2015 at 9:30 AM, Dmitry Torokhov > 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. > > I should have commented at that time, but let's do it now: I agree > with the idea, but this leaves the door open to confusing situations > in case gpiolib was unintentionally disabled. Could you also add a > note in the documentation of this function to explain this behavior, > to spare a few headaches to users of this function? You mean the inline documentation in drivers/gpio/gpiolib.c and drivers/gpio/devres.c? I can certainly mention there that is GPIOLIB is disabled thy will return NULL unlike the non-optional variants. > > > > > Signed-off-by: Dmitry Torokhov > > --- > > include/linux/gpio/consumer.h | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h > > index fd85cb1..f68244f 100644 > > --- a/include/linux/gpio/consumer.h > > +++ b/include/linux/gpio/consumer.h > > @@ -132,14 +132,14 @@ static inline struct gpio_desc *__must_check > > __gpiod_get_optional(struct device *dev, const char *con_id, > > enum gpiod_flags flags) > > { > > - return ERR_PTR(-ENOSYS); > > + return NULL; > > } > > > > static inline struct gpio_desc *__must_check > > __gpiod_get_index_optional(struct device *dev, const char *con_id, > > unsigned int index, enum gpiod_flags flags) > > { > > - return ERR_PTR(-ENOSYS); > > + return NULL; > > } > > > > static inline void gpiod_put(struct gpio_desc *desc) > > @@ -171,14 +171,14 @@ static inline struct gpio_desc *__must_check > > __devm_gpiod_get_optional(struct device *dev, const char *con_id, > > enum gpiod_flags flags) > > { > > - return ERR_PTR(-ENOSYS); > > + return NULL; > > } > > > > static inline struct gpio_desc *__must_check > > __devm_gpiod_get_index_optional(struct device *dev, const char *con_id, > > unsigned int index, enum gpiod_flags flags) > > { > > - return ERR_PTR(-ENOSYS); > > + return NULL; > > } > > > > static inline void devm_gpiod_put(struct device *dev, struct gpio_desc *desc) > > -- > > 2.2.0.rc0.207.ga3a616c > > > > > > -- > > Dmitry -- Dmitry