Messages in this thread | | | Subject | Re: Add skeleton "generic IO mapping" infrastructure. | From | David Woodhouse <> | Date | Tue, 14 Sep 2004 09:55:47 +0100 |
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On Mon, 2004-09-13 at 18:32 +0000, Linux Kernel Mailing List wrote: > ChangeSet 1.1869, 2004/09/13 11:32:00-07:00, torvalds@ppc970.osdl.org > > Add skeleton "generic IO mapping" infrastructure. > > Jeff wants to use this to clean up SATA and some network drivers.
> + * Read/write from/to an (offsettable) iomem cookie. It might be a PIO > + * access or a MMIO access, these functions don't care. The info is > + * encoded in the hardware mapping set up by the mapping functions > + * (or the cookie itself, depending on implementation and hw). > + * > + * The generic routines don't assume any hardware mappings, and just > + * encode the PIO/MMIO as part of the cookie. They coldly assume that > + * the MMIO IO mappings are not in the low address range. > + * > + * Architectures for which this is not true can't use this generic > + * implementation and should do their own copy. > + * > + * We encode the physical PIO addresses (0-0xffff) into the > + * pointer by offsetting them with a constant (0x10000) and > + * assuming that all the low addresses are always PIO. That means > + * we can do some sanity checks on the low bits, and don't > + * need to just take things for granted. > + */ > +#define PIO_OFFSET 0x10000 > +#define PIO_MASK 0x0ffff > +#define PIO_RESERVED 0x40000
> +#define IO_COND(addr, is_pio, is_mmio) do { \ > + unsigned long port = (unsigned long __force)addr; \ > + if (port < PIO_RESERVED) { \ > + VERIFY_PIO(port); \ > + port &= PIO_MASK; \ > + is_pio; \ > + } else { \ > + is_mmio; \ > + } \ > +} while (0)
Argh! Please no. You can't infer the IO space from the address. Provide a cookie containing {space, address} instead -- or indeed {bus, address}. Let some architectures optimise that by ignoring the bus and working it out from the address if you must, but don't put that in the generic version.
-- dwmw2
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