[Intel-gfx] [PATCH v2] pwm: lpss: Make builtin so that i915 can find the pwm_backlight

Thierry Reding thierry.reding at gmail.com
Fri Jan 20 10:42:10 UTC 2017

On Fri, Jan 20, 2017 at 11:18:29AM +0100, Hans de Goede wrote:
> Hi,
> On 20-01-17 10:55, Andy Shevchenko wrote:
> > On Fri, 2017-01-20 at 10:48 +0100, Hans de Goede wrote:
> > > I'm fine with doing a v3 with a comment, how about putting that
> > > comment
> > > right at all the module* stuff and explain there that that is to
> > > stay as the builtin only status is meant to be temporary ?
> > 
> > Can we do other way around? I mean that either i915 selects PWM_LPSS to
> > be built-in, or uses request_module() call?
> PWM_LPSS needs to be built-in if enabled, a stripped down kernel
> for non cherrytrail hardware does not need it ...
> Also (and esp for request_module) this means building knowledge
> into the i915 driver about which pwm hardware there is on which
> boards which is undesirable.
> Thierry, this does give me an idea though, what if we extend
> the info passed to pwm_add_table with a module-name and
> make pwm_get call request_module() ?

I'm not sure that's even necessary. request_module() forwards the string
you pass to it to the userspace helper, so you can pass things like the
modalias to it. I suspect that for ACPI the modalias could be trivially
derived from the provider name already in the table.

Or maybe it couldn't. We don't have information about the type of device
and the name doesn't match, or at least it would be much more difficult
to extend the same method to other types of devices. Module name doesn't
sound too bad, as long as it's optional.

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