Messages in this thread | | | Date | Fri, 10 Dec 2021 13:17:35 +0200 | From | Andy Shevchenko <> | Subject | Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk |
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On Thu, Dec 09, 2021 at 11:21:41PM +0300, Sergey Shtylyov wrote: > On 12/9/21 11:06 PM, Andy Shevchenko wrote: > > >> The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is > >> invalid") only calls WARN() when IRQ0 is about to be returned, however > >> using IRQ0 is considered invalid (according to Linus) outside the arch/ > >> code where it's used by the i8253 drivers. Many driver subsystems treat > >> 0 specially (e.g. as an indication of the polling mode by libata), so > >> the users of platform_get_irq[_byname]() in them would have to filter > >> out IRQ0 explicitly and this (quite obviously) doesn't scale... > >> Let's finally get this straight and return -EINVAL instead of IRQ0! > > > > You are changing the return value of platform_get_irq_optional(). > > The problem here is the proposed change doesn't bring any value in such > > case. platform_get_irq_optional() should be able (at the end of the day) > > to return 3 types of values (as other APIs do): > > > 0: success > > == 0: IRQ not found > > < 0: an error that must be consumed by the caller > > I remember that was in your patch that got reverted right after being merged. ;-) > IMHO returning both error code and 0 on failure is a sign of a misdesigned API, it > makes the failure check unnecessarily complex and error prone.
I dunno what you are talking about when you mentioned "0 on failure" because 0 is not the failure, that's what I'm trying to tell.
> > 0 is unexpected result for non-optional APIs and there you may try to play > > tricks (like replacing it by error code). > > > > There was a discussion around the topic: > > https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/T/#u > > I don't see much of the discussion there...
Indeed, it was split between two threads. Another one is this: https://lore.kernel.org/linux-serial/20210407101713.8694-1-andriy.shevchenko@linux.intel.com/T/#u
> > Wanna help? > > No, I'm afraid you're on your own here... > > >> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") > > > > Not sure. > > Why? It fixes gthe IRQ0 problem, so that you don't have to check for IRQ0 in many callers > (for the subsytems that treat 0 as s/th special, like polling mode)... If you have something > to improve, you can do that atop of this patch...
Because first we need to fix all users of platform_get_irq_optional().
-- With Best Regards, Andy Shevchenko
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