How to use a GPIO(libgpiod) with gpioget/gpioset, on i.MX8Q as an example difference between gpioget and "cat /sys/class/gpio" in GPIO control:
gpioget :
This is a command-line utility provided by the libgpiod library. It is designed to interact with GPIO lines through the modern Linux GPIO character device interface ( /dev/gpiochipN ).
/sys/class/gpio :
This refers to the legacy sysfs interface for GPIO control in Linux. While widely used in the past, this interface has been officially deprecated in favor of the libgpiod character device interface since Linux kernel version 6.0 and later.
Below is an example of libgpiod tested on i.MX8Q-MEK, L6.12.3 BSP.
Device tree settings:
We use GPIO1-05 and GPIO1-06 in this example. can put GPIO pinctrls in a specific group like “gpio_test”, or under certain driver like “gpio-keys”
gpio_test: gpio-test {
pinctrl-names = "default", "sleep";
pinctrl-0 = <&pinctrl_gpio_test_default>;
pinctrl-1 = <&pinctrl_gpio_test_sleep>;
status = "okay";
};
gpio-keys {
compatible = "gpio-keys";
pinctrl-names = "default", "sleep";
pinctrl-0 = <&pinctrl_gpio_example_default>;
pinctrl-1 = <&pinctrl_gpio_example_sleep>;
key_wakeup2{
label = "wakeup_key";
gpios = <&lsio_gpio2 1 GPIO_ACTIVE_LOW>;
linux,code = ;
wakeup-source;
};
pinctrl_gpio_test_default: gpiotestgrp_default {
fsl,pins = <
IMX8QM_LVDS0_I2C0_SDA_LSIO_GPIO1_IO07 0x06000061
IMX8QM_QSPI1A_DATA0_LSIO_GPIO4_IO26 0x06000041
IMX8QM_MIPI_CSI1_I2C0_SCL_LSIO_GPIO2_IO00 0x06000021
IMX8QM_LVDS0_I2C0_SCL_LSIO_GPIO1_IO06 0x06000021
>;
};
pinctrl_gpio_test_sleep: gpiotestgrp_sleep {
fsl,pins = <
IMX8QM_LVDS0_I2C0_SDA_LSIO_GPIO1_IO07 0x07800061
IMX8QM_QSPI1A_DATA0_LSIO_GPIO4_IO26 0x07800041
IMX8QM_MIPI_CSI1_I2C0_SCL_LSIO_GPIO2_IO00 0x07800021
IMX8QM_LVDS0_I2C0_SCL_LSIO_GPIO1_IO06 0x07800021
>;
};
pinctrl_gpio_example_default: gpioexamplegrp_default {
fsl,pins = <
IMX8QM_LVDS0_GPIO01_LSIO_GPIO1_IO05 0x06000021
IMX8QM_MIPI_CSI1_I2C0_SDA_LSIO_GPIO2_IO01 0x06000021
>;
};
pinctrl_gpio_example_sleep: gpioexamplegrp_sleep {
fsl,pins = <
IMX8QM_LVDS0_GPIO01_LSIO_GPIO1_IO05 0x07800021
IMX8QM_MIPI_CSI1_I2C0_SDA_LSIO_GPIO2_IO01 0x07800021
>;
};
Kernel commands to test GPIO function:
gpiodetect and gpioinfo command:
root@imx8qmmek:~# gpiodetect
gpiochip0 [5d080000.gpio] (32 lines)
gpiochip1 [5d090000.gpio] (32 lines)
gpiochip2 [5d0a0000.gpio] (32 lines)
gpiochip3 [5d0b0000.gpio] (32 lines)
gpiochip4 [5d0c0000.gpio] (32 lines)
gpiochip5 [5d0d0000.gpio] (32 lines)
gpiochip6 [5d0e0000.gpio] (32 lines)
gpiochip7 [5d0f0000.gpio] (32 lines)
root@imx8qmmek:~# gpioinfo -c 1
gpiochip1 - 32 lines:
line 0: unnamed input
line 1: unnamed input
line 2: unnamed input
line 3: unnamed input
line 4: unnamed input
line 5: unnamed input
line 6: unnamed output
line 7: unnamed output
line 8: unnamed input
line 9: unnamed input
line 10: unnamed input
line 11: unnamed input
line 12: unnamed input
line 13: unnamed output consumer=regulator-pcie
line 14: unnamed input
line 15: unnamed input
line 16: unnamed input
line 17: unnamed input
line 18: unnamed input
line 19: unnamed input
line 20: unnamed input
line 21: unnamed input
line 22: unnamed input
line 23: unnamed input
line 24: unnamed input
line 25: unnamed input
line 26: unnamed input
line 27: unnamed input
line 28: unnamed input
line 29: unnamed input
line 30: unnamed input
line 31: unnamed input
use cat /sys/kernel/debug/gpio to show current GPIO settings before GPIO1-05 and GPIO1-06 are set:
root@imx8qmmek:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-543, parent: platform/5d080000.gpio, 5d080000.gpio:
gpio-526 ( |scl ) out lo
gpio-527 ( |sda ) in lo
gpiochip1: GPIOs 544-575, parent: platform/5d090000.gpio, 5d090000.gpio:
gpio-557 ( |regulator-pcie ) out hi
gpiochip2: GPIOs 576-607, parent: platform/5d0a0000.gpio, 5d0a0000.gpio:
gpio-577 ( |wakeup_key ) in hi ACTIVE LOW
gpiochip3: GPIOs 608-639, parent: platform/5d0b0000.gpio, 5d0b0000.gpio:
gpio-618 ( |spi1 CS0 ) out hi ACTIVE LOW
gpiochip4: GPIOs 640-671, parent: platform/5d0c0000.gpio, 5d0c0000.gpio:
gpio-641 ( |enable ) out hi ACTIVE LOW
gpio-643 ( |regulator-usbotg1-vb) out lo
gpio-647 ( |usdhc2-vmmc ) out hi
gpio-667 ( |enable ) out lo ACTIVE LOW
gpio-668 ( |host-wake ) in hi ACTIVE LOW
gpio-669 ( |PCIe reset ) out hi ACTIVE LOW
gpiochip5: GPIOs 672-703, parent: platform/5d0d0000.gpio, 5d0d0000.gpio:
gpio-673 ( |mux ) out hi
gpio-693 ( |wp ) in lo
gpio-694 ( |cd ) in lo ACTIVE LOW
gpiochip6: GPIOs 704-735, parent: platform/5d0e0000.gpio, 5d0e0000.gpio:
gpiochip7: GPIOs 736-767, parent: platform/5d0f0000.gpio, 5d0f0000.gpio:
use gpioset command to set GPIO output, can also change GPIO direction(input → output)
#set gpiochip1-5 and 1-6
root@imx8qmmek:~# gpioset -c gpiochip1 6=1 &
[1] 700
root@imx8qmmek:~# gpioset -c gpiochip1 5=1 &
[2] 702
check the changes from the commands above with cat /sys/kernel/debug/gpio and gpioinfo -c 1 :
root@imx8qmmek:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-543, parent: platform/5d080000.gpio, 5d080000.gpio:
gpio-526 ( |scl ) out lo
gpio-527 ( |sda ) in lo
gpiochip1: GPIOs 544-575, parent: platform/5d090000.gpio, 5d090000.gpio:
gpio-549 ( |gpioset ) out hi
gpio-550 ( |gpioset ) out hi
gpio-557 ( |regulator-pcie ) out hi
gpiochip2: GPIOs 576-607, parent: platform/5d0a0000.gpio, 5d0a0000.gpio:
gpio-577 ( |wakeup_key ) in hi ACTIVE LOW
gpiochip3: GPIOs 608-639, parent: platform/5d0b0000.gpio, 5d0b0000.gpio:
gpio-618 ( |spi1 CS0 ) out hi ACTIVE LOW
gpiochip4: GPIOs 640-671, parent: platform/5d0c0000.gpio, 5d0c0000.gpio:
gpio-641 ( |enable ) out hi ACTIVE LOW
gpio-643 ( |regulator-usbotg1-vb) out lo
gpio-647 ( |usdhc2-vmmc ) out hi
gpio-667 ( |enable ) out lo ACTIVE LOW
gpio-668 ( |host-wake ) in hi ACTIVE LOW
gpio-669 ( |PCIe reset ) out hi ACTIVE LOW
gpiochip5: GPIOs 672-703, parent: platform/5d0d0000.gpio, 5d0d0000.gpio:
gpio-673 ( |mux ) out hi
gpio-693 ( |wp ) in lo
gpio-694 ( |cd ) in lo ACTIVE LOW
gpiochip6: GPIOs 704-735, parent: platform/5d0e0000.gpio, 5d0e0000.gpio:
gpiochip7: GPIOs 736-767, parent: platform/5d0f0000.gpio, 5d0f0000.gpio:
root@imx8qmmek:~# gpioinfo -c 1
gpiochip1 - 32 lines:
line 0: unnamed input
line 1: unnamed input
line 2: unnamed input
line 3: unnamed input
line 4: unnamed input
line 5: unnamed output consumer=gpioset
line 6: unnamed output consumer=gpioset
line 7: unnamed output
line 8: unnamed input
line 9: unnamed input
line 10: unnamed input
line 11: unnamed input
line 12: unnamed input
line 13: unnamed output consumer=regulator-pcie
How to enable legacy GPIO SYSFS(default disabled on L6 kernel and above)
refer to the comment of this commit:
https://github.com/nxp-imx/linux-imx/commit/3b4feb21158f873269ff3fbe2fe8d23a88d64b24
commit 3b4feb21158f873269ff3fbe2fe8d23a88d64b24
Author: Linus Walleij
Date: Tue Nov 10 15:27:24 2020 +0100
gpio: sysfs: Enforce character device
If users select sysfs support they get the character device
as well so that end-users cannot complain that they
"only have sysfs on my system". They should have the
character device at all times.
If someone is in so dire need of stripping out the
character device while still enabling the sysfs ABI they
can very well patch the kernel.
Also only show this obsolete option to expert users.
Signed-off-by: Linus Walleij
Link: <>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 5d4de5cd6759..4dd566f7ea39 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -59,8 +59,9 @@ config DEBUG_GPIO
that are most common when setting up new platforms or boards.
config GPIO_SYSFS
- bool "/sys/class/gpio/... (sysfs interface)"
+ bool "/sys/class/gpio/... (sysfs interface)" if EXPERT
depends on SYSFS
+ select GPIO_CDEV # We need to encourage the new ABI
help
Say Y here to add the legacy sysfs interface for GPIOs.
To enable GPIO_SYSFS, from the patch. The best way is CONFIG_EXPERT = y, then enable CONFIG_GPIO_SYSFS=Y. not need to revert the patch.
SYSFS, as legacy interface for GPIO control in Linux. While widely used in the past, this interface has been officially deprecated in favor of the libgpiod character device interface since Linux kernel version 6.0 and later. i.MX Processors
View full article
