Re: [RESEND][PATCH] watchdog: add support for Sigma Designs SMP86xx

[Guenter Roeck]

On 11/13/2015 10:02 AM, Måns Rullgård wrote:
> > > > > +static const struct of_device_id tangox_wdt_dt_ids[] = {
> > > > > +	{ .compatible = "sigma,smp8642-wdt" },
> > > >
> > > > So this is really for smp8642 only, not for any other chips in the series ?
> > >
> > > It's for about a dozen SMP86xx, SMP87xx, and SMP89xx chips.  Should I
> > > list them all?  I don't even know where to find a comprehensive list of
> > > device numbers.
> > I thought so, but I am not a devicetree expert, and I see some "xx" in
> > existing devicetree bindings. Something to ask when you submit the
> > bindings to the devicetree mailing list. Either case, I think it would
> > be either something like "sigma,smp86xx-wdt" or a list of all of them,
> > but not "sigma,smp8642-wdt" to be used for all chips.
>
> The general advice is to not use wildcards in DT bindings since the next
> chip matching the pattern might not be compatible at all.  New chips
> known to be compatible with an old one can specify both the exact chip
> and the older one such that existing drivers will work automatically.
> If at some point they are found not to be compatible after all (hardware
> bugs, perhaps) a fixed driver will work with existing device trees.
So I think the best approach here would be to list the chips known to work.

Thanks,
Guenter

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