Messages in this thread | | | Date | Tue, 14 Sep 2004 10:30:12 -0400 | From | Jeff Garzik <> | Subject | Re: Add skeleton "generic IO mapping" infrastructure. |
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David Woodhouse wrote: > 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.
Override it in your arch if you don't like the generic version ;-)
Jeff
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