Messages in this thread | | | Subject | Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk | From | Sergey Shtylyov <> | Date | Tue, 4 Jan 2022 22:27:58 +0300 |
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On 12/10/21 2:17 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.
OK.
>>> 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
OK.
>>> Wanna help? >> >> No, I'm afraid you're on your own here...
Tell me please, how far you've got with this by now? (I've already started to add the fixups to your patch -- unfortunately, this change has to be done atomically, not piecemeal.)
>>>> 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().
I still don't understand why your issue should be fixed 1st -- but I don't really care about the order...
MBR, Sergey
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