Hi Vishwanatha,
On 7/6/20 9:19 AM, Vishwanatha Subbanna wrote:
Hello,
I have been a user of “leds-gpio” driver to manage the LEDs on IBM servers. So far, all these LEDs that were controlled by GPIO were ACTIVE_LOW.
Example from DTS.
fan3 {
retain-state-shutdown;
default-state = "keep";
gpios = <&pca0 3 GPIO_ACTIVE_LOW>;
};
I wanted to know if it makes any difference to the user if the GPIO is ACTIVE_HIGH. I read through https://www.kernel.org/doc/Documentation/gpio/board.txt and it seemed we should be able to use it.
However, going through https://github.com/torvalds/linux/blob/master/drivers/leds/leds-pca955x.c, I am not quite sure if the ACTIVE_HIGH can be used same as ACTIVE_LOW since I saw these :
#define PCA955X_LS_LED_ON 0x0 /* Output LOW */
#define PCA955X_LS_LED_OFF 0x1 /* Output HI-Z */
#define PCA955X_GPO_HIGH LED_OFF
#define PCA955X_GPIO_LOW LED_FULL
This will be my DT entry :
fan3 {
retain-state-shutdown;
default-state = "keep";
gpios = <&pca0 3 GPIO_ACTIVE_HIGH>;
};
Will I be able to use the same “leds-gpio” interfaces irrespective of GPIO_LOW / GPIO_HIGH ?
I use these interfaces today:
echo 255 > brightness —> Turn Solid_ON
echo 0 > brightness —> Turn OFF
echo “timer” > trigger —> Initiate Blink
echo “none” > trigger —> Terminate Blink
From what I can see in gpiolib sources GPIO_ACTIVE_LOW results
in reversing the logic, i.e. pca955x_gpio_set_value() will
be passed 0 when setting gpio to 1.
Experience doesn't corroborate that?
--
Best regards,
Jacek Anaszewski
