From: Sergey Shtylyov <s.shtylyov@omp.ru>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Geert Uytterhoeven" <geert@linux-m68k.org>
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Subject: Re: [PATCH 1/2] platform: make platform_get_irq_optional() optional
Date: Wed, 19 Jan 2022 19:12:23 +0300 [thread overview]
Message-ID: <6370798a-7a7e-243d-99f9-09bf772ddbac@omp.ru> (raw)
In-Reply-To: <20220118142945.6y3rmvzt44pjpr4z@pengutronix.de>
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
next prev parent reply other threads:[~2022-01-19 16:12 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-10 19:54 [PATCH 0/2] Make platform_get_irq[_byname]_optional() optional Sergey Shtylyov
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
2022-01-18 14:29 ` Uwe Kleine-König
2022-01-19 16:12 ` Sergey Shtylyov [this message]
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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