Le Fri, 27 Jul 2012 09:59:21 +0200,
javier Martin [off-list ref] a ?crit :

Hi,
we are trying to support pinctrl for i.MX21, i.MX1 and i.MX27.

In these chips, gpio and pinctrl use the same HW memory area
registers. This means that we have to request the same memory area
from two different drivers (gpio and pinctrl) but we don't know how to
do that.

A similar example available is mxs, but it only works with device
tree, so this problem is avoided.  However, some of these chips
(i.MX21, i.MX1...) don't support device tree yet, so we need to
provide backwards compatibility.

What is the right way to request the same memory region from two
different drivers? Moreover, how can we guarantee that there won't be
any conflicts when accessing these shared resources?

I would say there is no right way. If the pinctrl/gpio registers are
really intermixed and belong to the same region, then there should be
only one driver that requests this region and that implements both the
pinctrl and gpio features.

See the drivers/pinctrl/pinctrl-coh901.c driver for example. It
implements both the pinctrl and the gpio logic.

Best regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com