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

[Guenter Roeck <linux@roeck-us.net>]

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