On Fri, Jul 12, 2024 at 03:29:21PM +0100, Eric Curtin wrote: > On Fri, 12 Jul 2024 at 15:13, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote: > > > > platform_get_irq() never returns zero so we can remove his dead code. > > Checking for zero is a historical artifact from over ten years ago. > > > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > There's quite a few return paths in platform_get_irq_optional, are we > sure it can never be zero? > > Not calling out a specific case here, but it's not so clear to me how > we can guarantee platform_get_irq() is never zero, > The platform_get_irq() function has a comment which describes how the error handling should work. I wrote a blog about this: https://staticthinking.wordpress.com/2023/08/07/writing-a-check-for-zero-irq-error-codes/ TLDR; platform_get_irq() used to return zero on error but it changed in 2006. I believe someone told me the historical situation was actually worse than I described where the error return wasn't always zero but depended on the arch so sometimes it was -1... Then after 2006 zero was success for a while because there was some hardware where zero was a valid IRQ. But now zero is not a valid IRQ. I think Linus has said that zero is a stupid IRQ number and support for that hardware was removed. So now it never returns zero and never will again. There are still some xxxxxxx_get_irq() which return zero on error, and those cause quite a bit of mixups. Last year there was even one which had a comment similar to platform_get_irq() that said to check for negatives but it returned zero on failure sometimes. :P regards, dan carpenter
