On Tue, May 1, 2012 at 7:28 AM, John Crispin <blogic@xxxxxxxxxxx> wrote: > On 30/04/12 19:54, David Daney wrote: >> On 04/30/2012 10:46 AM, John Crispin wrote: >>> On MIPS we want to call of_irq_map_pci from inside >>> >>> arch/mips/include/asm/pci.h:extern int pcibios_map_irq( >>> const struct pci_dev *dev, u8 slot, u8 pin); >>> >>> For this to work we need to change several functions to const usage. >> >> I think there is a mismatch on this throughout the kernel. >> >> Properly fixing it requires touching many more places than these. >> Although I haven't tried it, I wouldn't be surprised if doing this >> caused warnings to appear in non-MIPS code. >> >> Ralf had a patch at one point that tried to make this consistent >> tree-wide, but it is not yet applied. >> >> David Daney > > Hi, > > Ok, lets see what Ralf has to say. > > I just tested the patch on x86 with OF enabled and drivers turned on > that use the API. I did not see any errors appear. I'm far from a const expert, but I think this should be safe. Here's my reasoning: We're changing pci_swizzle_interrupt_pin() to take a pointer to a constant struct pci_dev. pci_swizzle_interrupt_pin() only reads the struct pci_dev; it doesn't modify it. It is legal to pass either "struct pci_dev *" or "const struct pci_dev *" to a function expecting "const struct pci_dev *"; the callee just won't be able to modify the struct, even if the caller can. Similar reasoning applies to of_irq_map_pci(). So I'm fine with this. You sent it to Grant, so I'll assume he'll merge it unless I hear otherwise. Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
