On Tue, Sep 10, 2013 at 11:44:05AM -0600, Stephen Warren wrote: > On 09/10/2013 11:04 AM, Mark Brown wrote: > > On Tue, Sep 10, 2013 at 09:07:43AM -0600, Stephen Warren wrote: > >> On 09/10/2013 04:09 AM, Mark Brown wrote: > > > >>> No. There are a couple of issues here. One is that we don't want > >>> to litter all drivers with conditional code to check if they > >>> actually got the regulator and so on, that's just pointless make > >>> work on the part of consumers. > > > >> So that's exactly the difference between (a) and (b) above. > > > > Right, but the idea is that we just only ignore a failure to get a > > supply if we can usefully run without that supply being present and > > there's more code there than simply ignoring the error - if the driver > > can genuinely just ignore all errors and otherwise not do anything > > different then requesting the regulator in the first place is clearly a > > waste of time and enabling it would be a waste of power. > > > > A driver should only be carrying code for a missing regulator if it can > > usefully work without it, like the cases where devices can use an > > internal reference if one is not available. > > OK, so I believe you're saying that the case of a chip with just a > single power source, which absolutely must be present in HW for the chip > to be powered, isn't appropriate for regulator_get_optional(). Something > must always define a regulator for that power source, even if there is > no external SW control over that power source. > I think you are supposed to use a dummy regulator in that case. Guenter > If so, how does a driver (or binding) that's been written without any > support for a regulator (since so far all boards have had no SW control > over that power source; it's always on) get enhanced to support boards > where there is SW control over the power source? > > We either allow the regulator to be optional (since SW control over the > regulator is optional), or go back to every board file and DT and add a > dummy regulator in (which then breaks DT ABI, and even ignoring that is > a pain). > > And note that when I say "optional" at the start of the previous > paragraph, I'm talking about probe-time regulator_get() operations and > DT content. Clearly as far as the rest of the driver is concerned, > something can always provide a dummy regulator so that e.g. > regulator_enable/disable() elsewhere always have something to operate > on. However, probe() either needs to call an API that automatically > provides such a dummy regulator, or open-code that itself. I'm still not > clear which option you think should be used. > -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
