Re: [RFC PATCH 3/7] i2c: allow DT nodes without 'compatible'

Alexandre Belloni
2020-03-12T11:44:37Z

On 12/03/2020 12:19:51+0100, Wolfram Sang wrote:
> > Clearly this does not fit the case reported by Alexandre: a device
> > having a driver which is known to be badly buggy, so we don't want to
> > instantiate it. But again, this should not affect DT as it is not
> > describing the HW, but only an implementation detail. Probably disabling
> > or blacklisting the driver would be a better option there?
>
> "Fixing the driver" is the first thing coming to my mind ;) But yeah,
> blacklisting would be another good solution. With only the information
> above, DT is not the right place to fix a broken driver.
>

To be clear, the driver is working properly but the HW isn't. It is a
PMIC and we need to avoid linux talking to it so the PMIC doesn't end up
killing the bus.

We end up with a node properly described in the device tree but with
status = "disabled". The relevance to the discussion was that you know
what is there and you want to avoid using its address.

See the pmic node on i2c1 in arch/arm/boot/dts/at91-sama5d3_xplained.dts
for what I'm referring to.

> > My apologies to Wolfram, I appreciate a lot the effort you are doing,
> > but before reviewing this patch I have never realized what I tried to
> > explain above.
>
> All good, Luca! Talking over code usually brings in viewpoints which
> have been missed so far. This is expected. Actually, I am very happy to
> have this discussion!
>
> All the best,
>
> Wolfram
>

--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering