Re: [PATCH 4/5] gpio: of: Add support to have multiple gpios in gpio-hog

From: Laxman Dewangan
Date: Wed Mar 09 2016 - 08:34:00 EST

On Wednesday 09 March 2016 11:58 AM, Markus Pargmann wrote:
* PGP Signed by an unknown key


On Tue, Mar 08, 2016 at 05:32:07PM +0530, Laxman Dewangan wrote:
The child node for gpio hogs under gpio controller's node
provide the mechanism to automatic GPIO request and
configuration as part of the gpio-controller's driver
probe function.

Currently, property "gpio" takes one gpios for such
configuration. Add support to have multiple GPIOs in
this property so that multiple GPIOs of gpio-controller
can be configured by this mechanism with one child node.
So if I read this correctly you want to have multiple GPIOs with the
same line name? Why don't you use multiple child nodes with individual
line names?

There is cases on which particular functional configuration needs sets of GPIO to set. On this case, making sub node for each GPIOs creates lots of sub-nodes and add complexity on readability, usability and maintainability.
Example: for my board, I wanted to set GPIO H2 to input and H0 and H1 to be output high.
Instead of three nodes, I can have two here:
gpio@0,6000d000 {
wlan_input {
gpios = <TEGRA_GPIO(H, 2) 0>;

wlan_output {
gpios = <TEGRA_GPIO(H, 0) 0 TEGRA_GPIO(H, 1) 0>;

So here I am grouping the multiple output GPIO together.

This looks much similar if we have many GPIOs for one type of configurations.

Even it looks better if we have something:
gpio@0,6000d000 {
wlan_control {
gpios-input = <TEGRA_GPIO(H, 2) 0>;
gpios-output-high = <TEGRA_GPIO(H, 0) 0 TEGRA_GPIO(H, 1) 0>;