| 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: Fri, 14 Jan 2022 22:14:10 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
CC: Mark Brown <broonie@...nel.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>,
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>,
"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
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>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
"open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
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>,
Takashi Iwai <tiwai@...e.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>,
Borislav Petkov <bp@...en8.de>,
Eric Auger <eric.auger@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
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>,
"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
<netdev@...r.kernel.org>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
Cornelia Huck <cohuck@...hat.com>,
"Linux MMC List" <linux-mmc@...r.kernel.org>,
Joakim Zhang <qiangqing.zhang@....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>,
"Sebastian Reichel" <sre@...nel.org>,
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 1/14/22 12:25 PM, Uwe Kleine-König wrote:
>>>>> 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/...
>
> Let me reformulate your statement to the IMHO equivalent:
>
> If you set aside the differences between
> platform_get_irq_optional() and gpiod_get_optional(),
Sorry, I should make it clear this is actually the diff between a would-be
platform_get_irq_optional() after my patch, not the current code...
> platform_get_irq_optional() is like gpiod_get_optional().
>
> The introduction of gpiod_get_optional() made it possible to simplify
> the following code:
>
> reset_gpio = gpiod_get(...)
> if IS_ERR(reset_gpio):
> error = PTR_ERR(reset_gpio)
> if error != -ENDEV:
ENODEV?
> return error
> else:
> gpiod_set_direction(reset_gpiod, INACTIVE)
>
> to
>
> reset_gpio = gpiod_get_optional(....)
> if IS_ERR(reset_gpio):
> return reset_gpio
> gpiod_set_direction(reset_gpiod, INACTIVE)
>
> and I never need to actually know if the reset_gpio actually exists.
> Either the line is put into its inactive state, or it doesn't exist and
> then gpiod_set_direction is a noop. For a regulator or a clk this works
> in a similar way.
>
> However for an interupt this cannot work. You will always have to check
> if the irq is actually there or not because if it's not you cannot just
> ignore that. So there is no benefit of an optional irq.
>
> Leaving error message reporting aside, the introduction of
> platform_get_irq_optional() allows to change
>
> irq = platform_get_irq(...);
> if (irq < 0 && irq != -ENXIO) {
> return irq;
> } else if (irq >= 0) {
Rather (irq > 0) actually, IRQ0 is considered invalid (but still returned).
> ... setup irq operation ...
> } else { /* irq == -ENXIO */
> ... setup polling ...
> }
>
> to
>
> irq = platform_get_irq_optional(...);
> if (irq < 0 && irq != -ENXIO) {
> return irq;
> } else if (irq >= 0) {
> ... setup irq operation ...
> } else { /* irq == -ENXIO */
> ... setup polling ...
> }
>
> which isn't a win. When changing the return value as you suggest, it can
> be changed instead to:
>
> irq = platform_get_irq_optional(...);
> if (irq < 0) {
> return irq;
> } else if (irq > 0) {
> ... setup irq operation ...
> } else { /* irq == 0 */
> ... setup polling ...
> }
>
> which is a tad nicer. If that is your goal however I ask you to also
> change the semantic of platform_get_irq() to return 0 on "not found".
Well, I'm not totally opposed to that... but would there be a considerable win?
Anyway, we should 1st stop returning 0 for "valid" IRQs -- this is done by my patch
the discussed patch series are atop of.
> Note the win is considerably less compared to gpiod_get_optional vs
If there's any at all... We'd basically have to touch /all/ platform_get_irq()
calls (and get an even larger CC list ;-)).
> gpiod_get however. And then it still lacks the semantic of a dummy irq
> which IMHO forfeits the right to call it ..._optional().
Not quite grasping it... Why e.g. clk_get() doesn't return 0 for a not found clock?
> Now I'm unwilling to continue the discussion unless there pops up a
> suggestion that results in a considerable part (say > 10%) of the
> drivers using platform_get_irq_optional not having to check if the
> return value corresponds to "not found".
Note that many actual drivers don't follow the pattern prescribed in the comment to
platform_get_irq_optional() and their check for an optional IRQ look like irq < 0
(and, after my patches, irq <= 0). Maybe we shouldn't even bother returning the error
codes and just return 0 for all kinds of misfortunes instead? :-)
> Best regards
> Uwe
MBR, Sergey
Powered by blists - more mailing lists