On 08/28/22 at 10:36am, Alexander Gordeev wrote: > On Sat, Aug 20, 2022 at 08:31:15AM +0800, Baoquan He wrote: > > Hi Baoquan, > > > arch_ioremap() return a bool, > > - IS_ERR means return an error > > - NULL means continue to remap > > - a non-NULL, non-IS_ERR pointer is returned directly > > arch_iounmap() return a bool, > > - 0 means continue to vunmap > > - error code means skip vunmap and return directly > > It would make more sense if the return values were described > from the prospective of an architecture, not the caller. > I.e true - unmapped, false - not supported, etc. Yes, sounds reasonable to me, thanks. While ChristopheL suggested to take another way. Please see below link. I will reply to Christophe to discuss that. https://lore.kernel.org/all/8df89136-a7f2-9b66-d522-a4fb9860bf22@xxxxxxxxxx/T/#u If the current arch_ioremap() way is taken, I will change the description as you said. > > > diff --git a/mm/ioremap.c b/mm/ioremap.c > > index 8652426282cc..99fde69becc7 100644 > > --- a/mm/ioremap.c > > +++ b/mm/ioremap.c > > @@ -17,6 +17,13 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, > > unsigned long offset, vaddr; > > phys_addr_t last_addr; > > struct vm_struct *area; > > + void __iomem *ioaddr; > > + > > + ioaddr = arch_ioremap(phys_addr, size, prot); > > + if (IS_ERR(ioaddr)) > > + return NULL; > > + else if (ioaddr) > > + return ioaddr; > > It seems to me arch_ioremap() could simply return an address > or an error. Then IOMEM_ERR_PTR(-ENOSYS) if the architecture > does not support it reads much better than the cryptic NULL. I may not follow. Returning NULL means arch_ioremap() doesn't give out a mapped address and doesn't encounter wrong thing. NULL is a little twisting, maybe '0' is better? > > Probably arch_iounmap() returning error would look better too, > though not sure about that. Don't follow either. arch_iounmap() is returning error now.
