Re: [GIT PULL] On-demand device probing

[Russell King - ARM Linux]

On Mon, Oct 19, 2015 at 04:29:40PM +0100, David Woodhouse wrote:
> I don't know that there *is* a coherent plan here to address it all.
> 
> Certainly, we *will* need subsystems to have firmware-specific
> knowledge in some cases. Take GPIO as an example; ACPI *has* a way to
> describe GPIO, and properties which reference GPIO pins are intended to
> work through that â while in DT, properties which reference GPIO pins
> will have different contents. They'll be compatible at the driver
> level, in the sense that there's a call to get a given GPIO given the
> property name, but the subsystems *will* be doing different things
> behind the scenes.

It's a bit ironic that you've chosen GPIO as an example there.  The
"new" GPIO API (the gpiod_* stuff) only has a fwnode way to get the
gpio descriptor.  There's no of_* method.

I'd like to use the gpiod_* stuff, but I feel that my options are
rather limited: either use fwnode_get_named_gpiod() with
&dev->of_node->fwnode, which seems like a hack by going underneath
the covers of how fwnode is (partially) implemented with DT, or by
using of_get_named_gpio() and the converting the gpio number to a
descriptor via gpio_to_desc().  Both feel very hacky.

If ACPI already handles GPIOs internally, then I'm left wondering
why GPIO descriptor stuff went down the fwnode route at all - it
seems rather pointless in this case, and it seems to make the use
of the gpiod* interfaces where we _do_ need to use it (DT) harder
and more hacky.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/