Message-ID: <29f0c65d-77f2-e5b2-f6cc-422add8a707d@omp.ru>
Date:   Thu, 13 Jan 2022 23:35:34 +0300
From:   Sergey Shtylyov <s.shtylyov@....ru>
To:     Mark Brown <broonie@...nel.org>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
CC:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        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>,
        Joakim Zhang <qiangqing.zhang@....com>,
        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>, <netdev@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.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>,
        Kamal Dasu <kdasu.kdev@...il.com>,
        "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>,
        Jaroslav Kysela <perex@...ex.cz>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Robert Richter <rric@...nel.org>,
        Saravanan Sekar <sravanhome@...il.com>,
        Corey Minyard <minyard@....org>,
        Linux PM list <linux-pm@...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>,
        Borislav Petkov <bp@...en8.de>,
        "Sebastian Reichel" <sre@...nel.org>,
        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>, Tony Luck <tony.luck@...el.com>,
        Mun Yew Tham <mun.yew.tham@...el.com>,
        Eric Auger <eric.auger@...hat.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.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 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>,
        "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 1/2] platform: make platform_get_irq_optional() optional

On 1/13/22 12:45 AM, Mark Brown wrote:

[...]
> (Do we really need *all* the CCs here?)

   Yeah, 25 files were changed and that resulted in 75 persons/lists addressed.
I didn't expect such a wide audience myself... :-)

>> That convinces me, that platform_get_irq_optional() is a bad name. The
>> only difference to platform_get_irq is that it's silent. And returning
>> a dummy irq value (which would make it aligned with the other _optional
>> functions) isn't possible.

> There is regulator_get_optional() which is I believe the earliest of
> these APIs, it doesn't return a dummy either (and is silent too) - this

   Hm, I'm seeing it's rather noisy... :-)

> is because regulator_get() does return a dummy since it's the vastly
> common case that regulators must be physically present and them not
> being found is due to there being an error in the system description.
> It's unfortunate that we've ended up with these two different senses for
> _optional(), people frequently get tripped up by it.
> 
>>> To me it sounds much more logical for the driver to check if an
>>> optional irq is non-zero (available) or zero (not available), than to
>>> sprinkle around checks for -ENXIO. In addition, you have to remember
>>> that this one returns -ENXIO, while other APIs use -ENOENT or -ENOSYS
>>> (or some other error code) to indicate absence. I thought not having
>>> to care about the actual error code was the main reason behind the
>>> introduction of the *_optional() APIs.
> 
>> No, the main benefit of gpiod_get_optional() (and clk_get_optional()) is
>> that you can handle an absent GPIO (or clk) as if it were available.

   Hm, I've just looked at these and must note that they match 1:1 with
platform_get_irq_optional(). Unfortunately, we can't however behave the
same way in request_irq() -- because it has to support IRQ0 for the sake
of i8253 drivers in arch/...
 
> Similarly for the regulator API, kind of.

MBR, Sergey

Powered by blists - more mailing lists