On Mon, Nov 18, 2013 at 01:57:27PM +0000, Mark Brown wrote: > On Mon, Nov 18, 2013 at 01:40:22PM +0000, Grant Likely wrote: > > > Some hardware does that. That's what OHCI, EHCI, UHCI, XHCI, SDHCI, and > > similar are all about. It always helps when well understood hardware > > follows a register interface. It doesn't work for everything, but I > > agree it would be good to have preferred hw interfaces for SPI & I2C. > > You'd need something class based like USB, there's such massive > variation in what the hardware is trying to do and the tradeoffs. A big > issue is that especially with I2C many of the devices are primarily > analogue devices implemnted in larger processes where the cost of adding > additional digital logic can have a noticeable effect on the area and > hence cost of the silicon. My comments were mostly regarding the interface controllers. Those which generate the same bus transactions but need different drivers on every SoC. I suspect that the same costs don't apply (or at least not to the same extent) to SoCs. Thierry
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