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 PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 19 Jan 2022 19:12:23 +0300 From: Sergey Shtylyov <s.shtylyov@....ru> To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, "Geert Uytterhoeven" <geert@...ux-m68k.org> CC: Andrew Lunn <andrew@...n.ch>, Ulf Hansson <ulf.hansson@...aro.org>, Vignesh Raghavendra <vigneshr@...com>, KVM list <kvm@...r.kernel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, <linux-iio@...r.kernel.org>, "Linus Walleij" <linus.walleij@...aro.org>, Amit Kucheria <amitk@...nel.org>, "ALSA Development Mailing List" <alsa-devel@...a-project.org>, Jaroslav Kysela <perex@...ex.cz>, Guenter Roeck <groeck@...omium.org>, Thierry Reding <thierry.reding@...il.com>, MTD Maling List <linux-mtd@...ts.infradead.org>, Linux I2C <linux-i2c@...r.kernel.org>, Miquel Raynal <miquel.raynal@...tlin.com>, <linux-phy@...ts.infradead.org>, linux-spi <linux-spi@...r.kernel.org>, Jiri Slaby <jirislaby@...nel.org>, "David S. Miller" <davem@...emloft.net>, Khuong Dinh <khuong@...amperecomputing.com>, Florian Fainelli <f.fainelli@...il.com>, Matthias Schiffer <matthias.schiffer@...tq-group.com>, Kamal Dasu <kdasu.kdev@...il.com>, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, Lee Jones <lee.jones@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, Daniel Lezcano <daniel.lezcano@...aro.org>, Kishon Vijay Abraham I <kishon@...com>, bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>, "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>, Jakub Kicinski <kuba@...nel.org>, Zhang Rui <rui.zhang@...el.com>, <platform-driver-x86@...r.kernel.org>, Linux PWM List <linux-pwm@...r.kernel.org>, Robert Richter <rric@...nel.org>, "Saravanan Sekar" <sravanhome@...il.com>, Corey Minyard <minyard@....org>, Linux PM list <linux-pm@...r.kernel.org>, Liam Girdwood <lgirdwood@...il.com>, "Mauro Carvalho Chehab" <mchehab@...nel.org>, John Garry <john.garry@...wei.com>, 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>, Takashi Iwai <tiwai@...e.com>, Matthias Brugger <matthias.bgg@...il.com>, <openipmi-developer@...ts.sourceforge.net>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Benson Leung <bleung@...omium.org>, Pengutronix Kernel Team <kernel@...gutronix.de>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, <linux-edac@...r.kernel.org>, "Tony Luck" <tony.luck@...el.com>, Richard Weinberger <richard@....at>, Mun Yew Tham <mun.yew.tham@...el.com>, Eric Auger <eric.auger@...hat.com>, netdev <netdev@...r.kernel.org>, "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, Cornelia Huck <cohuck@...hat.com>, "Linux MMC List" <linux-mmc@...r.kernel.org>, Joakim Zhang <qiangqing.zhang@....com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux-Renesas <linux-renesas-soc@...r.kernel.org>, Vinod Koul <vkoul@...nel.org>, "James Morse" <james.morse@....com>, Zha Qipeng <qipeng.zha@...el.com>, "Sebastian Reichel" <sre@...nel.org>, Niklas Söderlund <niklas.soderlund@...natech.se>, <linux-mediatek@...ts.infradead.org>, "Brian Norris" <computersforpeace@...il.com>, Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com> Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional On 1/18/22 5:29 PM, Uwe Kleine-König wrote: >> nst the magic not-found value (so no implementation detail magic >>>>> leaks into the caller code) and just pass it to the next API function= >> . >>>>> (And my expectation would be that if you chose to represent not-found= >> by >>>>> (void *)66 instead of NULL, you won't have to adapt any user, just th= >> e >>>>> framework internal checks. This is a good thing!) >>>> >>>> Ah, there is the wrong assumption: drivers sometimes do need to know >>>> if the resource was found, and thus do need to know about (void *)66, >>>> -ENODEV, or -ENXIO. I already gave examples for IRQ and clk before. >>>> I can imagine these exist for gpiod and regulator, too, as soon as >>>> you go beyond the trivial "enable" and "disable" use-cases. >>> >>> My premise is that every user who has to check for "not found" >>> explicitly should not use (clk|gpiod)_get_optional() but >>> (clk|gpiod)_get() and do proper (and explicit) error handling for >>> -ENODEV. (clk|gpiod)_get_optional() is only for these trivial use-cases. >>> >>>> And 0/NULL vs. > 0 is the natural check here: missing, but not >>>> an error. >>> >>> For me it it 100% irrelevant if "not found" is an error for the query >>> function or not. I just have to be able to check for "not found" and >>> react accordingly. >>> >>> And adding a function >>> >>> def platform_get_irq_opional(): >>> ret =3D platform_get_irq() >>> if ret =3D=3D -ENXIO: >>> return 0 >>> return ret >>> >>> it's not a useful addition to the API if I cannot use 0 as a dummy >>> because it doesn't simplify the caller enough to justify the additional >>> function. >>> >>> The only thing I need to be able is to distinguish the cases "there is >>> an irq", "there is no irq" and anything else is "there is a problem I >>> cannot handle and so forward it to my caller". The semantic of >>> platform_get_irq() is able to satisfy this requirement[1], so why introdu= >> ce >>> platform_get_irq_opional() for the small advantage that I can check for >>> not-found using >>> >>> if (!irq) >>> >>> instead of >>> >>> if (irq !=3D -ENXIO) >>> >>> ? The semantic of platform_get_irq() is easier ("Either a usable >>> non-negative irq number or a negative error number") compared to >>> platform_get_irq_optional() ("Either a usable positive irq number or a >>> negative error number or 0 meaning not found"). Usage of >>> platform_get_irq() isn't harder or more expensive (neither for a human >>> reader nor for a maching running the resulting compiled code). >>> For a human reader >>> >>> if (irq !=3D -ENXIO) >>> >>> is even easier to understand because for >>> >>> if (!irq) >>> >>> they have to check where the value comes from, see it's >>> platform_get_irq_optional() and understand that 0 means not-found. >> >> "vIRQ zero does not exist." > > With that statement in mind I would expect that a function that gives me > an (v)irq number never returns 0. > >>> This function just adds overhead because as a irq framework user I have >>> to understand another function. For me the added benefit is too small to >>> justify the additional function. And you break out-of-tree drivers. >>> These are all no major counter arguments, but as the advantage isn't >>> major either, they still matter. >>> >>> Best regards >>> Uwe >>> >>> [1] the only annoying thing is the error message. >> >> So there's still a need for two functions. > > Or a single function not emitting an error message together with the > callers being responsible for calling dev_err(). > > So the options in my preference order (first is best) are: > > - Remove the printk from platform_get_irq() and remove > platform_get_irq_optional(); Strong NAK here: - dev_err() in our function saves a lot of (repeatable!) comments; - we've already discussed that it's more optimal to check againt 0 than against -ENXIO in the callers. > - Rename platform_get_irq_optional() to platform_get_irq_silently() NAK as well. We'd better off complaining about irq < 0 in this function. > - Keep platform_get_irq_optional() as is NAK, it's suboptimal in the call sites. > - Collect underpants > > - ? You're on your own here. :-) > - Change semantic of platform_get_irq_optional() Yes, we should change the semantics if it serves our goals better. > Best regards > Uwe MBR, Sergey
Powered by blists - more mailing lists