Stephen,
On Wed, Feb 13, 2013 at 1:04 PM, Stephen Warren <swar...@wwwdotorg.org> wrote: > On 02/13/2013 11:02 AM, Doug Anderson wrote: >> We need to use the i2c-arbitrator to talk to any of the devices on i2c >> bus 4 on exynos5250-snow so that we don't confuse the embedded >> controller (EC). Add the i2c-arbitrator to the device tree. As we >> add future devices (keyboard, sbs, tps65090) we'll add them on top of >> this. >> >> The arbitrated bus is numbered 104 simply as a convenience to make it >> easier for people poking around to guess that it might have something >> to do with the physical bus 4. >> >> The addition is split between the cros5250-common and the snow device >> tree file since not all cros5250-class devices use arbitration. > >> diff --git a/arch/arm/boot/dts/cros5250-common.dtsi >> b/arch/arm/boot/dts/cros5250-common.dtsi > >> i2c@12CA0000 { >> - status = "disabled"; >> + samsung,i2c-sda-delay = <100>; >> + samsung,i2c-max-bus-freq = <66000>; > > Shouldn't that use the standard clock-frequency property? At the moment this is the way that you specify it for the i2c controller we're using... >> diff --git a/arch/arm/boot/dts/exynos5250-snow.dts >> b/arch/arm/boot/dts/exynos5250-snow.dts > >> + i2c-arbitrator { >> + compatible = "i2c-arbitrator"; >> + #address-cells = <1>; >> + #size-cells = <0>; > >> + /* Use ID 104 as a hint that we're on physical bus 4 */ >> + i2c_104: i2c@0 { > > Does something use that hint? It sounds a little odd. The i2c bus numbering patches will end up creating "/dev/i2c-104". ...so the hint is really for developers who are poking around. It's definitely a strange number and that's part of the point. Right now there's nothing preventing someone from using 'i2cdetect' or 'i2cget' on bus 4 and bypassing arbitration. My hope was that having something crazy like "104" would help someone realize that it's a bad idea. ...besides, if I don't come up with _some_ number then this will get assigned the first unused ID which could be extra confusing. -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/