Messages in this thread | | | Date | Thu, 21 Sep 2006 02:30:17 -0400 | From | Jeff Garzik <> | Subject | Re: [patch 3/3] Add tsi108 On Chip Ethernet device driver support |
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Zang Roy-r61911 wrote: > On Thu, 2006-09-21 at 12:26, Jeff Garzik wrote: >> Zang Roy-r61911 wrote: >>> +#define TSI108_ETH_WRITE_REG(offset, val) \ >>> + writel(le32_to_cpu(val),data->regs + (offset)) >>> + >>> +#define TSI108_ETH_READ_REG(offset) \ >>> + le32_to_cpu(readl(data->regs + (offset))) >>> + >>> +#define TSI108_ETH_WRITE_PHYREG(offset, val) \ >>> + writel(le32_to_cpu(val), data->phyregs + (offset)) >>> + >>> +#define TSI108_ETH_READ_PHYREG(offset) \ >>> + le32_to_cpu(readl(data->phyregs + (offset))) >> >> NAK: >> >> 1) writel() and readl() are defined to be little endian. >> >> If your platform is different, then your platform should have its own >> foobus_writel() and foobus_readl(). > > Tsi108 bridge is designed for powerpc platform. Originally, I use > out_be32() and in_be32(). While there is no obvious reason to object > using this bridge in a little endian system. Maybe some extra hardware > logic needed for the bus interface. le32_to_cpu() can be aware the > endian difference.
To restate, readl() should read a little endian value, and return a CPU-endian value. writel() should receive a CPU-endian value, and write a little endian value.
If your platform's readl/writel doesn't do that, it's broken.
That's why normal PCI drivers can use readl() and writel() on either big-endian or little-endian machines, without needing to use le32_to_cpu().
Jeff
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