[PATCH v8 3/9] pci: Introduce pci_register_io_range() helper function.

Liviu Dudau
2014-07-01T20:45:09Z

On Tue, Jul 01, 2014 at 09:36:10PM +0200, Arnd Bergmann wrote:
> On Tuesday 01 July 2014 19:43:28 Liviu Dudau wrote:
> > +/*
> > + * Record the PCI IO range (expressed as CPU physical address + size).
> > + * Return a negative value if an error has occured, zero otherwise
> > + */
> > +int __weak pci_register_io_range(phys_addr_t addr, resource_size_t size)
> > +{
> > +#ifdef PCI_IOBASE
> > + struct io_range *res;
> > + resource_size_t allocated_size = 0;
> > +
> > + /* check if the range hasn't been previously recorded */
> > + list_for_each_entry(res, &io_range_list, list) {
> > + if (addr >= res->start && addr + size <= res->start + size)
> > + return 0;
> > + allocated_size += res->size;
> > + }
> > +
> > + /* range not registed yet, check for available space */
> > + if (allocated_size + size - 1 > IO_SPACE_LIMIT)
> > + return -E2BIG;
> > +
> > + /* add the range to the list */
> > + res = kzalloc(sizeof(*res), GFP_KERNEL);
> > + if (!res)
> > + return -ENOMEM;
> > +
> > + res->start = addr;
> > + res->size = size;
> > +
> > + list_add_tail(&res->list, &io_range_list);
> > +
> > + return 0;
> > +#else
> > + return -EINVAL;
> > +#endif
> > +}
> > +
> > unsigned long __weak pci_address_to_pio(phys_addr_t address)
> > {
> > +#ifdef PCI_IOBASE
> > + struct io_range *res;
> > + resource_size_t offset = 0;
> > +
> > + list_for_each_entry(res, &io_range_list, list) {
> > + if (address >= res->start &&
> > + address < res->start + res->size) {
> > + return res->start - address + offset;
> > + }
> > + offset += res->size;
> > + }
> > +
> > + return (unsigned long)-1;
> > +#else
> > if (address > IO_SPACE_LIMIT)
> > return (unsigned long)-1;
> >
> > return (unsigned long) address;
> > +#endif
> > }
>
> This still conflicts with the other allocator you have in patch 9
> for pci_remap_iospace: nothing guarantees that the mapping is the
> same for both.
>
> Also, this is a completely pointless exercise at this moment, because
> nobody cares about the result of pci_address_to_pio on architectures
> that don't already provide this function. If we ever get a proper
> Open Firmware implementation that wants to put hardcoded PCI devices
> into DT, we can add an implementation, but for now this seems overkill.
>
> The allocator in pci_register_io_range seems reasonable, why not merge
> this function with pci_remap_iospace() as I have asked you multiple
> times before? Just make it return the io_offset so the caller can
> put that into the PCI host resources.

Hi Arnd,

While I agree with you that at some moment the allocators were inconsistent
wrt each other, for this version I would respectfully disagree on this.
The allocator in pci_register_io_range() only makes sure that the ranges
are not overlapping, it doesn't do any mapping whatsoever, while
pci_remap_iospace() does only an ioremap_page_range(). The idea is that
you get the offset out of pci_address_to_pio() and apply it to
pci_remap_iospace().

Why do you think there are conflicts?

Best regards,
Liviu

>
> Arnd
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