On Tue, 2015-11-03 at 12:08 +0100, Philipp Zabel wrote:

Hi YH,

Am Dienstag, den 03.11.2015, 16:11 +0800 schrieb YH Huang:

quoted

quoted

The reasoning is that devices where there is no phandle link pointing to
the backlight (for example from a simple-panel node), we should keep the
current default behaviour (enable during probe).

I have a little problem for the current default behaviour.
Should we enable during probe?

Here I mean enabling the backlight (at the end of the probe function),
not enabling the GPIO already when requesting it.

quoted

Before this patch ( http://patchwork.ozlabs.org/patch/324690/ ),
we disable "enable-gpio" in the probe function.

While before this patch the GPIO would be initialized in the disabled
state, the call to backlight_update_status at the end of the probe
function would still enable the backlight afterwards.

Based on this, could we disable it initially and update in the
backlight_update_status function?

Like this,

if (pb->enable_gpio) {
	if (phandle &&
	    gpiod_get_direction(pb->enable_gpio) = GPIOF_DIR_OUT &&
	    gpiod_get_value(pb->enable_gpio) = 1)
		gpiod_direction_output(pb->enable_gpio, 1);
	else
		gpiod_direction_output(pb->enable_gpio, 0);
}

And then update with props.brightness in backlight_update_status.
I am not sure, maybe I miss something.

Regards,
YH Huang