Re: [PATCH v2] mtd: nand: document the NAND controller/NAND chip DT representation

Boris Brezillon
2016-04-02T13:48:06Z

Hi Brian,

On Fri, 1 Apr 2016 13:57:22 -0700
Brian Norris <computersforpeace@gmail.com> wrote:

> On Fri, Apr 01, 2016 at 02:26:35PM +0200, Boris Brezillon wrote:
> > Standardize the NAND controller/NAND chip DT representation. Now, all new
> > NAND controller drivers should comply with this representation, even if
> > they are only supporting a single NAND chip.
> >
> > Existing drivers can keep support for the old representation (where only
> > the NAND chip was described), but are encouraged to also support the new
> > one.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---
> > Changes since v1:
> > - fix typo
> > ---
>
> Thanks for doing this. This mostly looks pretty good.
>
> > Documentation/devicetree/bindings/mtd/nand.txt | 37 +++++++++++++++++++++++++-
> > 1 file changed, 36 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/mtd/nand.txt b/Documentation/devicetree/bindings/mtd/nand.txt
> > index b53f92e..a17662b 100644
> > --- a/Documentation/devicetree/bindings/mtd/nand.txt
> > +++ b/Documentation/devicetree/bindings/mtd/nand.txt
> > @@ -1,4 +1,23 @@
> > -* MTD generic binding
> > +* NAND chip and NAND controller generic binding
> > +
> > +NAND controller/NAND chip representation:
>
> You're starting with an assumption that there is a difference. I suppose
> that's usually the case, but is there ever a case that there isn't
> really? For instance, what about gpio.c? It's just a few GPIOs wired
> directly to a NAND chip.

Well, even if it's a bit-banging controller which is able to only
interface with a single chip it's still a controller and not the NAND
chip itself, so I think keeping the separation in this case is still
valid. As an example, see the i2c or spi bit-banging drivers, even if
there's no real controller, they are still represented with their own
node...

> Or perhaps, does it make sense still, even
> there? For instance, if you wanted to wire multiple chips but share most
> of the lines, you'd need to coordinate this in a "controller" node
> somehow.

Yep.

>
> All-in-all, looks good though, and we can patch this up with any other
> additions. (It's not exactly a formal specification, after all, but just
> guidelines.) So:
>
> Acked-by: Brian Norris <computersforpeace@gmail.com>

Ok, I'll wait for an ack from a DT maintainer before taking this patch.

Thanks,

Boris

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering