1. LED是用keypad 的backlight LED
2. GPIO 為INPUT (似按button後導通)
整體行為:
當GPIO為 PULL_HIGH時, LED亮
當GPIO為 PULL_DOWN時, LED滅
相關的driver code:
kernel/drivers/led/led-class.c, led-core.c, leds-qpnp.c, led-triggers.c, ledtrig-gpio.c
看完code可發現, 此功能若依kernel的code 只能用 device node的設定來變更GPIO的pin值,
無法用devicetree 來直接指定 (所以此文是修改啟動script來設定GPIO pin number)
1. 開啟 kernel 功能 (修改 default_config 檔: kernel/arch/arm/configs/msm8974_defconfig )
加入:
CONFIG_LEDS_QPNP=y
CONFIG_LEDS_TRIGGERS=y
CONFIG_LEDS_TRIGGER_BACKLIGHT=y
CONFIG_LEDS_TRIGGER_GPIO=y
CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
2. 設定GPIO行為 (修改 kernel/arch/arm/mach-msm/board-msm8974-gpiomux.c)
static struct gpiomux_setting button_act_cfg = {
.func = GPIOMUX_FUNC_GPIO,
.drv = GPIOMUX_DRV_2MA,
.pull = GPIOMUX_PULL_NONE,
.dir = GPIOMUX_IN,
};
static struct gpiomux_setting button_sus_cfg = {
.func = GPIOMUX_FUNC_GPIO,
.drv = GPIOMUX_DRV_2MA,
.pull = GPIOMUX_PULL_DOWN,
};
static struct msm_gpiomux_config msm_BUTTON_config[] __initdata = {
{
.gpio = GPIO_BUTTON, //79
.settings = {
[GPIOMUX_ACTIVE] = &button_act_cfg,
[GPIOMUX_SUSPENDED] = &button_sus_cfg,
},
},
};
void __init msm_msmd8974_init_gpiomux(void)
{
...
msm_gpiomux_install(msm_BUTTON_config, ARRAY_SIZE(msm_BUTTON_config));
}
3. 設定 LED與指定用GPIO觸發 (kernel/arch/arm/boot/dts/msm8974-leds.dtsi)
&pm8941_lsid1 {
...
qcom,leds@e200 {
...
qcom,kpdbl4 {
label = "kpdbl";
linux,name = "kpdbl-pwm-4";
qcom,mode = "pwm";
qcom,pwm-channel = <11>;
qcom,pwm-us = <1000>;
qcom,id = <7>;
qcom,max-current = <20>;
qcom,row-id = <3>;
qcom,row-src-en;
qcom,always-on;
qcom,default-state = "off";
linux,default-trigger = "gpio";
};
4. 指定GPIO 值與設定亮度等, 這部份自己找 啟動scripts 放, 我是放在 (device/qcom/common/rootdir/etc/init.qcom.sh)
echo gpio > /sys/class/leds/kpdbl-pwm-4/trigger
echo 255 > /sys/class/leds/kpdbl-pwm-4/desired_brightness
echo 255 > /sys/class/leds/kpdbl-pwm-4/brightness
echo 79 > /sys/class/leds/kpdbl-pwm-4/gpio
