Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk

From: Sergey Shtylyov
Date: Wed Jan 12 2022 - 12:54:01 EST


On 1/4/22 12:26 PM, Marc Zyngier wrote:

> [Adding Geert]
>
> On Sat, 06 Nov 2021 20:26:47 +0000,
> Sergey Shtylyov <s.shtylyov@xxxxxx> 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!
>>
>> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
>> Signed-off-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
>>
>> ---
>> The patch is against the 'driver-core-linus' branch of Greg Kroah-Hartman's
>> 'driver-core.git' repo.
>>
>> drivers/base/platform.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> Index: driver-core/drivers/base/platform.c
>> ===================================================================
>> --- driver-core.orig/drivers/base/platform.c
>> +++ driver-core/drivers/base/platform.c
>> @@ -231,7 +231,8 @@ int platform_get_irq_optional(struct pla
>> out_not_found:
>> ret = -ENXIO;
>> out:
>> - WARN(ret == 0, "0 is an invalid IRQ number\n");
>> + if (WARN(!ret, "0 is an invalid IRQ number\n"))
>> + return -EINVAL;
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(platform_get_irq_optional);
>> @@ -445,7 +446,8 @@ static int __platform_get_irq_byname(str
>>
>> r = platform_get_resource_byname(dev, IORESOURCE_IRQ, name);
>> if (r) {
>> - WARN(r->start == 0, "0 is an invalid IRQ number\n");
>> + if (WARN(!r->start, "0 is an invalid IRQ number\n"))
>> + return -EINVAL;
>> return r->start;
>> }
>
> Geert recently mentioned that a few architectures (such as sh?) still
> use IRQ0 as something valid in limited cases.
>
> From my PoV, this patch is fine, but please be prepared to fix things
> in a couple of years when someone decides to boot a recent kernel on
> their pet dinosaur. With that in mind:
>
> Acked-by: Marc Zyngier <maz@xxxxxxxxxx>

Greg, so would that ACK be enough? Is there a chance this patch gets finally included
into 5.17-rc1? Or should I look into fixing the recently found arch/sh/ issue 1st (as you
can see, just WARN()'ing about IRQ0 wasn't enough to get this fixed)?

> M.

MBR, Sergey