Messages in this thread | | | Date | Sun, 26 Jan 2014 12:39:21 +0000 | From | Mark Brown <> | Subject | Re: Using an optional regulator in a driver running on a PC |
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On Sun, Jan 26, 2014 at 02:53:07AM -0800, Guenter Roeck wrote:
> This leads to an interesting question: How are drivers which require > regulators (optional or not) supposed to run on a system > which does not support devicetree, and does not have any > regulators installed (such as a PC) ? REGULATOR_DUMMY > isn't there anymore, and the dummy code it replaces only > executes on devicetree based systems.
A feature like regulator_get_optional() can only work if we know about all the regulator mappings that exist which with the current way of registering mappings via platform data we can only do once regulators have been registered. This is a bit unfortunate and is why we never used to have get_optional().
> Also, how are non-dt systems supposed to determine if an optional > regulator exists or not ? AFAICS the regulator code always returns > -EPROBE_DEFER, which isn't very helpful. If I just assume that > -EPROBE_DEFER means that the regulator is not there, I end up with > a conflict with a system which _does_ support devicetree, where > -EPROBE_DEFER really means that the probe needs to be deferred.
It's nothing to do with devicetree, other systems can do it if they specify full constraints. All the core is doing is saying that it might get told about more registrations later and not knowing if the regulator might appear or not it's going with a conservative report. Other platforms need to either call regulator_have_full_constraints() when they've registered all the mappings or do something else (OF is doing the something else because it embeds the lookup code into the regulator framework rather than translating and registering the mappings at boot time).
I think platforms like PCs need to add a new way of registering mappings outside of regulator registrations and then use those especially for things like regulators on PCI cards. [unhandled content-type:application/pgp-signature] | |