Hi,

On Thu, Dec 04, 2014 at 11:15:38PM +0900, Alexandre Courbot wrote:

On Wed, Dec 3, 2014 at 1:12 AM, Maxime Ripard
[off-list ref] wrote:

quoted

On Tue, Dec 02, 2014 at 03:29:46PM +0100, Linus Walleij wrote:

quoted

On Tue, Dec 2, 2014 at 3:13 PM, Alexandre Courbot [off-list ref] wrote:

quoted

On Tue, Dec 2, 2014 at 1:36 AM, Maxime Ripard
[off-list ref] wrote:

quoted

quoted

The only thing I'd like to have would be that the request here would
be non-exclusive, so that a later driver would still be allowed later
on to request that GPIO later on and manage it itself (ideally using
the usual gpiod_request function).

Actually we have a plan (and I have some code too) to allow multiple
consumers per GPIO. Although like Benoit I wonder why you would want
to hog a GPIO and then request it properly later. Also, that probably
means we should abandon the hog since it actively drives the line and
would interfere with the late requested. How to do that correctly is
not really clear to me.

I don't get the usecase. A hogged GPIO is per definition hogged.
This sounds more like "initial settings" or something, which is another
usecase altogether.

We do have one board where we have a pin (let's say GPIO14 of the bank
A) that enables a regulator that will provide VCC the bank B.

Now, both banks are handled by the same driver, but in order to have a
working output on the bank B, we do need to set GPIO14 as soon as
we're probed.

Just relying on the usual deferred probing introduces a circular
dependency between the gpio-regulator that needs to grab its GPIO from
a driver not there yet, and the gpio driver that needs to enable its
gpio-regulator.

I don't get it. According to what you said, the following order should
go through IIUC:

1) bank A is probed, gpio 14 is available
2) gpio-regulator is probed, acquires GPIO 14, regulator for Bank B is available
3) bank B is probed, grabs its regulator and turn it on, probes.

What am I missing?

It would be true if bank A and B were exposed through different
drivers (or at least different instances of the same driver), which is
not the case.

In our case, banks A and B are handled by the same instance.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com