Re: [PATCH] spi: Force the registration of the spidev devices

Geert Uytterhoeven
2014-05-05T14:23:00Z

Hi Alexandre,

On Mon, May 5, 2014 at 3:57 PM, Alexandre Belloni
<alexandre.belloni@free-electrons.com> wrote:
> On 05/05/2014 at 09:10:43 +0200, Geert Uytterhoeven wrote :
>> On Mon, May 5, 2014 at 6:17 AM, Maxime Ripard
>> <maxime.ripard@free-electrons.com> wrote:
>> > On Fri, May 02, 2014 at 01:28:26AM +0200, Geert Uytterhoeven wrote:
>> >> On Fri, May 2, 2014 at 12:36 AM, Maxime Ripard
>> >> <maxime.ripard@free-electrons.com> wrote:
>> >> > But it actually doesn't work in a case where you can't really predict
>> >> > what is on the other side of the bus. Either because, on the board
>> >> > you're using the pins are exposed and it's pretty much up to the user
>> >> > to know what to put on it. That could be handled by DT overlays
>> >> > though.
>> >> >
>> >> > What never works is where the device on the other side is so generic
>> >> > that you really can't tell what it does. Think of a microcontroller
>> >> > that would behave as a SPI slave. It's behaviour and what it does is
>> >> > pretty much dependant of what we flashed on it, and suddenly the
>> >> > compatible string is not the proper reprensentation anymore.
>> >>
>> >> So you will (hopefully soon) use overlay DT to change the DTS to match what's
>> >> connected?
>> >
>> > Not really, because you can't declare a spidev device in the DT.
>>
>> Yes you can. I've done it before.
>>
>> See also "git grep -w spidev -- arch/arm/*/dts/".
>
> I'm pretty sure that doesn't work as there is no compatible matching
> "spidev"

See the last line of spi_match_device():

return strcmp(spi->modalias, drv->name) == 0;

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