linux-kernel - Re: [PATCH 1/2] platform: make platform_get_irq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 10 Jan 2022 21:10:14 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, linux-iio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Amit Kucheria <amitk@...nel.org>, alsa-devel@...a-project.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sebastian Reichel <sre@...nel.org>,
        linux-phy@...ts.infradead.org,
        Thierry Reding <thierry.reding@...il.com>,
        linux-mtd@...ts.infradead.org, linux-i2c@...r.kernel.org,
        linux-gpio@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Guenter Roeck <groeck@...omium.org>,
        Lee Jones <lee.jones@...aro.org>,
        openipmi-developer@...ts.sourceforge.net,
        Saravanan Sekar <sravanhome@...il.com>,
        Khuong Dinh <khuong@...amperecomputing.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Matthias Schiffer <matthias.schiffer@...tq-group.com>,
        kvm@...r.kernel.org, Kamal Dasu <kdasu.kdev@...il.com>,
        Richard Weinberger <richard@....at>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-serial@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        platform-driver-x86@...r.kernel.org, linux-pwm@...r.kernel.org,
        John Garry <john.garry@...wei.com>,
        Robert Richter <rric@...nel.org>,
        Zha Qipeng <qipeng.zha@...el.com>,
        Corey Minyard <minyard@....org>, linux-pm@...r.kernel.org,
        Peter Korsgaard <peter@...sgaard.com>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Mark Gross <markgross@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Mark Brown <broonie@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-edac@...r.kernel.org,
        Tony Luck <tony.luck@...el.com>,
        Mun Yew Tham <mun.yew.tham@...el.com>,
        Eric Auger <eric.auger@...hat.com>, netdev@...r.kernel.org,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Cornelia Huck <cohuck@...hat.com>, linux-mmc@...r.kernel.org,
        Joakim Zhang <qiangqing.zhang@....com>,
        linux-spi@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Vinod Koul <vkoul@...nel.org>,
        James Morse <james.morse@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        linux-mediatek@...ts.infradead.org,
        Brian Norris <computersforpeace@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional

Hello,

On Mon, Jan 10, 2022 at 10:54:48PM +0300, Sergey Shtylyov wrote:
> This patch is based on the former Andy Shevchenko's patch:
> 
> https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/
> 
> Currently platform_get_irq_optional() returns an error code even if IRQ
> resource simply has not been found. It prevents the callers from being
> error code agnostic in their error handling:
> 
> 	ret = platform_get_irq_optional(...);
> 	if (ret < 0 && ret != -ENXIO)
> 		return ret; // respect deferred probe
> 	if (ret > 0)
> 		...we get an IRQ...
> 
> All other *_optional() APIs seem to return 0 or NULL in case an optional
> resource is not available. Let's follow this good example, so that the
> callers would look like:
> 
> 	ret = platform_get_irq_optional(...);
> 	if (ret < 0)
> 		return ret;
> 	if (ret > 0)
> 		...we get an IRQ...

The difference to gpiod_get_optional (and most other *_optional) is that
you can use the NULL value as if it were a valid GPIO.

As this isn't given with for irqs, I don't think changing the return
value has much sense. In my eyes the problem with platform_get_irq() and
platform_get_irq_optional() is that someone considered it was a good
idea that a global function emits an error message. The problem is,
that's only true most of the time. (Sometimes the caller can handle an
error (here: the absence of an irq) just fine, sometimes the generic
error message just isn't as good as a message by the caller could be.
(here: The caller could emit "TX irq not found" which is a much nicer
message than "IRQ index 5 not found".)

My suggestion would be to keep the return value of
platform_get_irq_optional() as is, but rename it to
platform_get_irq_silent() to get rid of the expectation invoked by the
naming similarity that motivated you to change
platform_get_irq_optional().

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)