Thanks for your answer, Yes I added these 2 lines in the config.txt file like for the raspbain . 
So What do I have to do with the dtb files. I see nothing regarding the spi. 
Do I still have to use the config.txt file ? 
Thanks for your help.

2017-09-16 14:57 GMT+02:00 Peter Robinson <pbrobinson@gmail.com>:
On Sat, Sep 16, 2017 at 1:33 PM, christophe pages <pageschrist@gmail.com> wrote:
> Hello,
> I try to activate the spi on my raspberry3 using a fedora 26.
> I tried these options:
> device_tree_param=spi=on
> dtoverlay=spi-bcm2708

Did you add that to config.txt? That way of doing it is specific to
Rasspian, the driver in Fedora is the upstream driver which is
spi-bcm2835aux and you'll need to either edit the dtb to enable it or
use a DT overlay as it's disabled by default.

> I use this kernel:
> 4.12.5-300.fc26.armv7hl
>
> I see that the support in kernel seems already inside:
> CONFIG_SPI=y
> # CONFIG_SPI_DEBUG is not set
> CONFIG_SPI_MASTER=y
>
>
> But I never see the devices /dev/spi* appearing.
> I can't see any messages regarding spi in dmesg.
>
> I tested with a raspbian and I see them correctly.
> I think I miss somethiing.
> Could you help.
> Thanks.
>
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