Date:   Sun, 16 Jan 2022 00:06:00 +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>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        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>, Jiri Slaby <jirislaby@...nel.org>,
        <openipmi-developer@...ts.sourceforge.net>,
        "Khuong Dinh" <khuong@...amperecomputing.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Matthias Schiffer <matthias.schiffer@...tq-group.com>,
        Joakim Zhang <qiangqing.zhang@....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>,
        "Tony Luck" <tony.luck@...el.com>,
        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>,
        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>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        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>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Mark Brown <broonie@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "Sebastian Reichel" <sre@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        "Matthias Brugger" <matthias.bgg@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        <platform-driver-x86@...r.kernel.org>,
        Benson Leung <bleung@...omium.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        <linux-edac@...r.kernel.org>,
        Mun Yew Tham <mun.yew.tham@...el.com>,
        "Hans de Goede" <hdegoede@...hat.com>,
        netdev <netdev@...r.kernel.org>,
        "Yoshihiro Shimoda" <yoshihiro.shimoda.uh@...esas.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        "Liam Girdwood" <lgirdwood@...il.com>,
        linux-spi <linux-spi@...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>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Richard Weinberger <richard@....at>,
        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] driver core: platform: Rename platform_get_irq_optional()
 to platform_get_irq_silent()

On 1/15/22 6:21 PM, Uwe Kleine-König wrote:

[...]
>>>>>> The subsystems regulator, clk and gpio have the concept of a dummy
>>>>>> resource. For regulator, clk and gpio there is a semantic difference
>>>>>> between the regular _get() function and the _get_optional() variant.
>>>>>> (One might return the dummy resource, the other won't. Unfortunately
>>>>>> which one implements which isn't the same for these three.) The
>>>>>> difference between platform_get_irq() and platform_get_irq_optional() is
>>>>>> only that the former might emit an error message and the later won't.
>>>>
>>>>    This is only a current difference but I'm still going to return 0 ISO
>>>> -ENXIO from latform_get_irq_optional(), no way I'd leave that -ENXIO there
>>>> alone... :-)
>>>
>>> This would address a bit of the critic in my commit log. But as 0 isn't
>>> a dummy value like the dummy values that exist for clk, gpiod and
>>> regulator I still think that the naming is a bad idea because it's not
>>> in the spirit of the other *_get_optional functions.
>>>
>>> Seeing you say that -ENXIO is a bad return value for
>>> platform_get_irq_optional() and 0 should be used instead, I wonder why
>>> not changing platform_get_irq() to return 0 instead of -ENXIO, too.
>>> This question is for now only about a sensible semantic. That actually
>>> changing platform_get_irq() is probably harder than changing
>>> platform_get_irq_optional() is a different story.
>>>
>>> If only platform_get_irq_optional() is changed and given that the
>>> callers have to do something like:
>>>
>>>         if (this_irq_exists()):
>>>                 ... (e.g. request_irq)
>>>         else:
>>>                 ... (e.g. setup polling)
>>>
>>> I really think it's a bad idea that this_irq_exists() has to be
>>> different for platform_get_irq() vs. platform_get_irq_optional().
>>
>> For platform_get_irq(), the IRQ being absent is an error condition,
>> hence it should return an error code.
>> For platform_get_irq_optional(), the IRQ being absent is not an error
>> condition, hence it should not return an error code, and 0 is OK.
> 
> Please show a few examples how this simplifies the code. If it's only

   As for platform_get_irq(), returning -ENXIO simplifies things a lot: you don't
have to check for 0 at every freaking call site and have s/th like (every
time!):

	irq = platform_get_irq();
	if (irq <= 0)
		return irq ?: -ENXIO; // any error code you choose

instead of just:

	irq = platform_get_irq();
	if (irq < 0)
		return irq;

This scales better in my book.

> that a driver has to check for == 0 instead of == -ENXIO, than that's
> not a good enough motivation to make platform_get_irq_optional()
> different to platform_get_irq().

   Again, it scales better... good motivation in my eyes.

> Best regards
> Uwe

MBR, Sergey

Powered by blists - more mailing lists