Re: [RFC 4/4] ARM: shmobile: r8a7790: adapt DTS for I2C slave support

Geert Uytterhoeven
2014-09-12T10:10:46Z

Hi Wolfram,

On Fri, Sep 12, 2014 at 11:58 AM, Wolfram Sang <wsa@the-dreams.de> wrote:
> 2) Slave mode is needed for board bringup
>
> Some other components need a specific I2C slave to be present before
> userspace is available, otherwise the system is unusable. This is IMO
> then a hardware description and justifies DT entries:

OK, I didn't think this case, which is similar to an external device requiring
a GPIO to be at a specific level.

> DT pseudocode:
>
> i2c {
> compatible = "nvidia, tegra-i2c";
>
> ec-slave@42 {
> compatible = "nvidia, ax100-ec-slave";
> reg = <0x42>;
> };
> };

So distinguishing between drivers providing slave services (using slave
mode) and drivers driving actual slave hardware (using master mode) is
done based on the compatible-property.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds