From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
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Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional
Date: Tue, 18 Jan 2022 13:49:15 +0100 [thread overview]
Message-ID: <CAMuHMdWkwV9XE_R5FZ=jPtDwLpDbEngG6+X2JmiDJCZJZvUjYA@mail.gmail.com> (raw)
In-Reply-To: <20220118120806.pbjsat4ulg3vnhsh@pengutronix.de>
Hi Uwe,
On Tue, Jan 18, 2022 at 1:08 PM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> On Tue, Jan 18, 2022 at 10:37:25AM +0100, Geert Uytterhoeven wrote:
> > On Tue, Jan 18, 2022 at 10:09 AM Uwe Kleine-König
> > <u.kleine-koenig@pengutronix.de> wrote:
> > > For the (clk|gpiod|regulator)_get_optional() you don't have to check
> > > against 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 the
> > > 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 = platform_get_irq()
> if ret == -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 introduce
> platform_get_irq_opional() for the small advantage that I can check for
> not-found using
>
> if (!irq)
>
> instead of
>
> if (irq != -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 != -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."
> 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.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2022-01-18 12:49 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220110195449.12448-1-s.shtylyov@omp.ru>
2022-01-10 19:54 ` [PATCH 1/2] platform: make platform_get_irq_optional() optional Sergey Shtylyov
2022-01-10 20:10 ` Uwe Kleine-König
2022-01-10 21:07 ` Andy Shevchenko
2022-01-10 21:44 ` Uwe Kleine-König
2022-01-10 21:18 ` Andrew Lunn
2022-01-12 8:33 ` Geert Uytterhoeven
2022-01-12 8:50 ` Uwe Kleine-König
2022-01-12 10:27 ` Geert Uytterhoeven
2022-01-12 12:27 ` Andy Shevchenko
2022-01-12 13:38 ` Andrew Lunn
2022-01-12 13:51 ` Andy Shevchenko
2022-01-12 13:54 ` Geert Uytterhoeven
2022-01-12 14:41 ` Rafael J. Wysocki
2022-01-12 15:05 ` Sergey Shtylyov
2022-01-12 15:13 ` Hans de Goede
2022-01-12 15:48 ` Rafael J. Wysocki
2022-01-12 16:21 ` Andy Shevchenko
2022-01-12 21:31 ` Uwe Kleine-König
2022-01-12 21:45 ` Mark Brown
2022-01-13 11:08 ` Uwe Kleine-König
2022-01-13 14:45 ` Mark Brown
2022-01-13 19:43 ` [PATCH] driver core: platform: Rename platform_get_irq_optional() to platform_get_irq_silent() Uwe Kleine-König
2022-01-13 20:17 ` Mark Brown
2022-01-13 20:57 ` Sergey Shtylyov
2022-01-13 22:43 ` Uwe Kleine-König
2022-01-14 9:58 ` Geert Uytterhoeven
2022-01-15 15:21 ` Uwe Kleine-König
2022-01-15 21:06 ` Sergey Shtylyov
2022-01-14 11:34 ` Sergey Shtylyov
2022-01-13 20:31 ` Guenter Roeck
2022-01-13 21:42 ` Florian Fainelli
2022-01-13 23:06 ` Uwe Kleine-König
2022-01-14 17:55 ` Sergey Shtylyov
2022-01-15 13:55 ` Uwe Kleine-König
2022-01-19 18:36 ` Andy Shevchenko
2022-01-19 19:44 ` Sergey Shtylyov
2022-01-19 18:40 ` Andy Shevchenko
2022-01-14 6:57 ` Peter Korsgaard
2022-01-14 13:04 ` Andy Shevchenko
2022-01-15 15:45 ` Uwe Kleine-König
2022-01-19 18:51 ` Andy Shevchenko
2022-01-19 19:47 ` Sergey Shtylyov
2022-01-19 20:55 ` Andy Shevchenko
2022-01-20 7:57 ` Uwe Kleine-König
2022-01-24 15:01 ` Andy Shevchenko
2022-01-24 21:02 ` Sergey Shtylyov
2022-01-25 8:25 ` Geert Uytterhoeven
2022-01-25 12:56 ` Matthias Schiffer
2022-01-25 14:01 ` Andy Shevchenko
2022-01-14 19:45 ` Sergey Shtylyov
2022-01-14 20:29 ` Uwe Kleine-König
2022-01-15 13:08 ` Sergey Shtylyov
2022-01-19 18:52 ` Andy Shevchenko
2022-01-13 20:35 ` [PATCH 1/2] platform: make platform_get_irq_optional() optional Sergey Shtylyov
2022-01-14 9:25 ` Uwe Kleine-König
2022-01-14 9:39 ` Geert Uytterhoeven
2022-01-14 19:14 ` Sergey Shtylyov
2022-01-14 20:22 ` Uwe Kleine-König
2022-01-15 20:22 ` Sergey Shtylyov
2022-01-17 8:41 ` Geert Uytterhoeven
2022-01-17 9:24 ` Uwe Kleine-König
2022-01-17 10:35 ` Geert Uytterhoeven
2022-01-17 11:49 ` Uwe Kleine-König
2022-01-17 13:08 ` Geert Uytterhoeven
2022-01-17 17:06 ` Uwe Kleine-König
2022-01-18 8:25 ` Geert Uytterhoeven
2022-01-18 9:09 ` Uwe Kleine-König
2022-01-18 9:37 ` Geert Uytterhoeven
2022-01-18 12:08 ` Uwe Kleine-König
2022-01-18 12:49 ` Geert Uytterhoeven [this message]
2022-01-18 14:29 ` Uwe Kleine-König
2022-01-19 16:12 ` Sergey Shtylyov
2022-01-19 18:29 ` Sergey Shtylyov
2022-01-20 11:27 ` Sergey Shtylyov
2022-01-16 18:15 ` Sergey Shtylyov
2022-01-17 8:47 ` Uwe Kleine-König
2022-01-18 20:21 ` Sergey Shtylyov
2022-01-18 22:26 ` Uwe Kleine-König
2022-01-19 15:34 ` Sergey Shtylyov
2022-01-19 18:58 ` Andy Shevchenko
2022-01-19 19:49 ` Sergey Shtylyov
2022-01-14 18:46 ` Sergey Shtylyov
2022-01-15 18:36 ` [PATCH 1/2] platform: make platform_get_irq_optional() optional (summary) Uwe Kleine-König
2022-01-16 14:19 ` Greg Kroah-Hartman
2022-01-18 9:18 ` Uwe Kleine-König
2022-01-18 9:32 ` Greg Kroah-Hartman
2022-01-19 10:56 ` Sergey Shtylyov
2022-01-19 11:33 ` Uwe Kleine-König
2022-01-19 11:42 ` Sergey Shtylyov
2022-01-19 19:06 ` Andy Shevchenko
2022-01-17 11:57 ` [PATCH 1/2] platform: make platform_get_irq_optional() optional Sergey Shtylyov
2022-01-19 15:02 ` Uwe Kleine-König
2022-01-19 15:50 ` Sergey Shtylyov
2022-01-10 19:54 ` [PATCH 2/2] platform: make platform_get_irq_byname_optional() optional Sergey Shtylyov
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