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Re: [PATCH] gpio: 74x164: add dt support for nxp's 74x594

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  Re: [PATCH] gpio: 74x164: add dt support for nxp's 74x594 Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-22 12:00 +0100
    Re: [PATCH] gpio: 74x164: add dt support for nxp's 74x594 Nicolas Saenz Julienne <nicolassaenzj@gmail.com> - 2016-03-23 00:20 +0100

#1362529 — Re: [PATCH] gpio: 74x164: add dt support for nxp's 74x594

Hi Nicolas,

On Tue, Mar 22, 2016 at 11:42 AM, nicolas saenz julienne
<nicolassaenzj@gmail.com> wrote:
>> Why did you choose the "lvc" variant?
> Well to be honest the HW people did and it's all I could test with.  I don't
> know much about these naming schemes, apart from the intuition it has to do
> with frequency and line levels.
>
>> Ideally, you want to put the oldest "manuf,74x594" variant here.
> What do you mean by oldest? What would you suggest? it's funny because the chip
> is going to be used on a new product that is meant to be produced for years.

For DT bindings, it doesn't matter who manufactured the part, or which
technology was used (TTL, HC, LVC, ...).

Logically, the shiny new parts are compatible with the old ones, from as early
as the 1960s.

Especially for standard logic glue, where you can source parts from several
manufacturers, and which are available in many different technologies, it
doesn't make much sense to have all combinations in the DT bindings.

https://en.wikipedia.org/wiki/7400_series

Now, which one to pick?
Given the precedence set by the existing compatible value "fairchild,74hc595",
perhaps the most logical one to add is "fairchild,74hc594"?

Or can we just drop the manufacturer?

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

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#1363102

Hi Geert, thanks for your reply.

On Tue, Mar 22, 2016 at 11:56:51AM +0100, Geert Uytterhoeven wrote:
[..]
> For DT bindings, it doesn't matter who manufactured the part, or which
> technology was used (TTL, HC, LVC, ...).
> 
> Logically, the shiny new parts are compatible with the old ones, from as early
> as the 1960s.
> 
> Especially for standard logic glue, where you can source parts from several
> manufacturers, and which are available in many different technologies, it
> doesn't make much sense to have all combinations in the DT bindings.
> 
> https://en.wikipedia.org/wiki/7400_series
That did the trick.

> 
> Now, which one to pick?
> Given the precedence set by the existing compatible value "fairchild,74hc595",
> perhaps the most logical one to add is "fairchild,74hc594"?
> 
> Or can we just drop the manufacturer?
Well as you say DT doesn't care for technology nor manufacturer. I'd go for
dropping the manufacturer and adding an "x" for the technology (i.e. 74x595).
I saw that the binding is being used on some boards is there any rule against
changing bindings that are already being used?

> 
> 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
I'll happily do a new version of the patch if the idea is worth it.

	Nicolas

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