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

[Laxman Dewangan]

On Wednesday 09 March 2016 11:58 AM, Markus Pargmann wrote:
> * PGP Signed by an unknown key
>
> Hi,
>
> 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 {
                       gpio-hog;
                       gpios = <TEGRA_GPIO(H, 2) 0>;
                       input;
               };

               wlan_output {
                       gpio-hog;
                       gpios = <TEGRA_GPIO(H, 0) 0 TEGRA_GPIO(H, 1) 0>;
                       output-high;
               };
       };

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 {
                       gpio-hog;
                       gpios-input = <TEGRA_GPIO(H, 2) 0>;
                       gpios-output-high = <TEGRA_GPIO(H, 0) 0 
TEGRA_GPIO(H, 1) 0>;
               };
       };