Re: [RFC PATCH 2/2] asm-generic: Add new pci.h and use it

From: Arnd Bergmann
Date: Fri Jul 15 2022 - 04:39:23 EST

On Thu, Jul 14, 2022 at 11:46 PM Stafford Horne <shorne@xxxxxxxxx> wrote:
> The asm/pci.h used for many newer architectures share similar
> definitions. Move the common parts to asm-generic/pci.h to allow for
> sharing code.

This looks very nice, thanks for doing it!

> Two things to note are:
> - isa_dma_bridge_buggy, traditionally this is defined in asm/dma.h but
> these architectures avoid creating that file and add the definition
> to asm/pci.h.

I would prefer if we could just kill off this variable for non-x86, as it's
only set to a nonzero value in two implementations that are both
x86-specific and most of the references are gone. That does not have
to be part of this series though, if you don't want to address it here, just
add a comment to the new pci.h file.

> - ARCH_GENERIC_PCI_MMAP_RESOURCE, csky does not define this so we
> undefine it after including asm-generic/pci.h. Why doesn't csky
> define it?

Adding David Woodhouse to Cc, as he introduced this interface. As I
understand it, this was meant as a replacement for the old
architecture specific pci_mmap_page_range interface, and is ideally
used everywhere.

It's probably something that slipped through the review of csky and
should have been there.

As an aside, it seems the pci_mmap_page_range() cleanup was
left almost complete, with sparc being the only one left after
David Miller found a problem with the generic code. Not sure if
this was ever resolved:

> +#ifndef PCIBIOS_MIN_IO
> +#define PCIBIOS_MIN_IO 0
> +#endif
> +
> +#define PCIBIOS_MIN_MEM 0

We should probably #ifdef both of these for consistency.

> +static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)
> +{
> + /* no legacy ide irq support */
> + return -ENODEV;
> +}

And this can just go away now, according to what we found.