On Wed, May 13, 2015 at 09:10:48PM +0200, Geert Uytterhoeven wrote: > On Wed, May 13, 2015 at 2:51 PM, Maxime Ripard > <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > >> > This also adds an i2cdev-like feeling, where you get all the > >> > spidev devices all the time, without any modification. > >> > >> I2C is a bit safer here since it's a shared bus so you can't do > >> anything to devices not connected to the bus by mistake. > > > > I'm not sure to understand what you mean here. How is SPI different > > from that aspect? > > If you talk to a nonexistent i2c device, nothing happens, as it just sends > a message with a nonexistent address on the shared bus. > > If you talk to a nonexistent spi device, hell may break loose if e.g. some > "smart" hardware engineer used the "unused" CS as a pull-up for the > _RESET line on an external device... It's a bit like banging random > "unused" GPIOs. Ah, right. I'm always surprised by how creative the hardware engineers actually are :) Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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