On Thu, Mar 10, 2016 at 1:59 PM, Gregor Riepl <onitake@xxxxxxxxx> wrote: >> 1) It is strange, but it looks that via Vanilla custom x8_64 Linux >> 4.4.2 ArchLinux Baytrail on Chuwi Vi10 the Touchscreen Control Chip >> probably resides not on 0x48 and it is resides on i2c-3 0x30. This >> confused me completely, AFAIK chip could switch buses but not its >> address. >> Will be happy if anyone helps with this - whether it is possible for >> chip to be i2c-4, 0x48 on Android and switched in Linux to i2c-3 0x30? > > The way I2C works, this is simply not possible unless the chip is reconfigured > somehow. I2C frames always start with the device address, and if a chip isn't > listening for a specific address (or a broadcast), it will not respond. > > The I2C bus number in user space on the other hand is completely dynamic and > depends on the driver load order. > > So in short, without any separate "switching" mechanism (highly unlikely), the > device will always have the same address (0x30 is 48 in decimal, mind you), > but it may live on i2c-0, i2c-1, i2c-2, i2c-3, i2c-4, i2c-5 depending on when > the bus is initialised or which drivers are loaded. Some devices do allow you to switch slave address, Goodix touchscreen is one example. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
