From: Sergey Shtylyov <s.shtylyov@omp.ru>
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: Sun, 16 Jan 2022 21:15:20 +0300 [thread overview]
Message-ID: <57af1851-9341-985e-7b28-d2ba86770ecb@omp.ru> (raw)
In-Reply-To: <20220114202226.ugzklxv4wzr6egwj@pengutronix.de>
Hello!
On 1/14/22 11:22 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...
>
> The similarity is that with your patch both gpiod_get_optional() and
> platform_get_irq_optional() return NULL and 0 on not-found. The relevant
> difference however is that for a gpiod NULL is a dummy value, while for
> irqs it's not. So the similarity is only syntactically, but not
> semantically.
I have noting to say here, rather than optional IRQ could well have a different
meaning than for clk/gpio/etc.
[...]
>>> 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).
>
> This is a topic I don't feel strong for, so I'm sloppy here. If changing
> this is all that is needed to convince you of my point ...
Note that we should absolutely (and first of all) stop returning 0 from platform_get_irq()
on a "real" IRQ0. Handling that "still good" zero absolutely doesn't scale e.g. for the subsystems
(like libata) which take 0 as an indication that the polling mode should be used... We can't afford
to be sloppy here. ;-)
[...]
> Best regards
> Uwe
MBR, Sergey
next prev parent reply other threads:[~2022-01-16 18:15 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
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 [this message]
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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