Re: [PATCH] spi: spidev: Warn loudly if instantiated from DT as "spidev"

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

On Thu, Apr 23, 2015 at 9:21 AM, Martin Sperl <kernel@xxxxxxxxxxxxxxxx> wrote:
>> On 28.03.2015, at 00:42, Mark Brown <broonie@xxxxxxxxxx> wrote:
>>
>> Since spidev is a detail of how Linux controls a device rather than a
>> description of the hardware in the system we should never have a node
>> described as "spidev" in DT, any SPI device could be a spidev so this
>> is just not a useful description.
>>
>> In order to help prevent users from writing such device trees generate a
>> warning if spidev is instantiated as a DT node without an ID in the match
>> table.
>>
>> Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
>
> So what is now the “correct way” to create a spidev device via the
> device-tree?

Add the compatible value for your device to the spidev_dt_ids[] array in
drivers/spi/spidev.c.

> Note that on a raspberry pi the 2 SPI devices are by default configured
> as spidev and only overlays would change the settings to a different
> alias. So this change will impact that default immediately.
>
> Thus I wonder if it is wise to produce potential “support issues" for
> distributions triggered by this patch.

So what you need is a way to handover from generic spidev to a device-specific
driver, cfr. what graphics drivers do when the device has been bound to by
vesafb or simplefb.

Could this be implemented in a generic way in the spi or DT code?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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
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