From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752195Ab3LJDLC (ORCPT ); Mon, 9 Dec 2013 22:11:02 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:11360 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751910Ab3LJDLA (ORCPT ); Mon, 9 Dec 2013 22:11:00 -0500 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Mon, 09 Dec 2013 19:07:39 -0800 Message-ID: <52A68640.5010806@nvidia.com> Date: Tue, 10 Dec 2013 12:10:56 +0900 From: Alex Courbot Organization: NVIDIA User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: Andy Shevchenko CC: Linus Walleij , Mika Westerberg , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] gpiolib: return -ENOENT when no GPIO mapping exists References: <1386295616-14192-1-git-send-email-acourbot@nvidia.com> <1386584927.1871.127.camel@smile> In-Reply-To: <1386584927.1871.127.camel@smile> X-NVConfidentiality: public Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/09/2013 07:28 PM, Andy Shevchenko wrote: > On Fri, 2013-12-06 at 11:06 +0900, Alexandre Courbot wrote: >> Some devices drivers make use of optional GPIO parameters. For such >> drivers, it is important to discriminate between the case where no >> GPIO mapping has been defined for the function they are requesting, and >> the case where a mapping exists but an error occured while resolving it >> or when acquiring the GPIO. >> >> This patch changes the family of gpiod_get() functions such that they >> will return -ENOENT if and only if no GPIO mapping is defined for the >> requested function. Other error codes are used when an actual error >> occured during the GPIO resolution. >> > > I like the idea. > One minor comment below (in code). > >> Signed-off-by: Alexandre Courbot >> --- >> I think this change should be merged early as not having it may prevent >> some users to switch to gpiod. I stumbled upon this issue while >> considering porting a simple driver (pwm_bl) that has an optional GPIO >> parameter. >> >> Mika, Andy: if Linus agrees with this change, could you take care of >> having -ENOENT returned as well for the ACPI and SFI GPIOs lookup? > > I have already switched to -ENOENT, so, consider done. Great, thanks! >> My understanding of ACPI was not sufficient to allow me to do it myself. >> SFI OTOH should be trivial as it is a simple table. >> >> Documentation/gpio/consumer.txt | 6 +++++- >> drivers/gpio/gpiolib.c | 31 ++++++++++++++++--------------- >> 2 files changed, 21 insertions(+), 16 deletions(-) >> >> diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt >> index 07c74a3765a0..e42f77d8d4ca 100644 >> --- a/Documentation/gpio/consumer.txt >> +++ b/Documentation/gpio/consumer.txt >> @@ -38,7 +38,11 @@ device that displays digits), an additional index argument can be specified: >> const char *con_id, unsigned int idx) >> >> Both functions return either a valid GPIO descriptor, or an error code checkable >> -with IS_ERR(). They will never return a NULL pointer. >> +with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned >> +if and only if no GPIO has been assigned to the device/function/index triplet, >> +other error codes are used for cases where a GPIO has been assigned but an error >> +occured while trying to acquire it. This is useful to discriminate between mere >> +errors and an absence of GPIO for optional GPIO parameters. >> >> Device-managed variants of these functions are also defined: >> >> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c >> index 5fad38fcd701..e96d4a90c0c3 100644 >> --- a/drivers/gpio/gpiolib.c >> +++ b/drivers/gpio/gpiolib.c >> @@ -2358,7 +2358,7 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, >> unsigned int idx, >> enum gpio_lookup_flags *flags) >> { >> - struct gpio_desc *desc = ERR_PTR(-ENODEV); >> + struct gpio_desc *desc = ERR_PTR(-ENOENT); >> struct gpiod_lookup_table *table; >> struct gpiod_lookup *p; >> >> @@ -2380,19 +2380,21 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, >> chip = find_chip_by_name(p->chip_label); >> >> if (!chip) { >> - dev_warn(dev, "cannot find GPIO chip %s\n", >> - p->chip_label); >> - continue; >> + dev_err(dev, "cannot find GPIO chip %s\n", >> + p->chip_label); >> + return ERR_PTR(-ENODEV); >> } >> >> if (chip->ngpio <= p->chip_hwnum) { >> - dev_warn(dev, "GPIO chip %s has %d GPIOs\n", >> - chip->label, chip->ngpio); >> - continue; >> + dev_err(dev, "requested GPIO %d but chip %s has %d\n", > > The proposed message may confuse user. This lead to question in my head: > "what gpio chip has that referred by %d at the end of line". > > Maybe something like "requested GPIO %d is out of range [0..%d] for chip > %s\n" ? I agree it would be better. My concern here is to have the line fit within 80 characters. :P But you're right, I will improve this in v2. Thanks, Alex.