How GPIO input buttons read through sys file and updating in Device tree in SDK 7(3.12)

shankar naragoni

Hi all,

I am currently using SDK 7.00 for am335x custom board, I am trying to read the value of an input. I am using kernel 3.12 kernel. The only way I have found is to manually export the gpio and then read the value but i want read gpio buttons through sys. here i am using pre defined gpio drive gpio_keys.c. find the device tree bellow...

gpio_keys_s0: gpio_keys_s0 {
                        pinctrl-single,pins = <
                                0x2c (PIN_INPUT_PULLUP | MUX_MODE7)   /*key_init GPIO0_27 */
                                0x20 (PIN_INPUT_PULLUP | MUX_MODE7)   /* Alaram_key GPIO0_22 */
                                0x28 (PIN_INPUT_PULLUP | MUX_MODE7)   /* Cancel_key GPIO0_26---- 0x28 */
                                0x24 (PIN_INPUT_PULLUP | MUX_MODE7)   /* Away_key GPIO0_23 */
                        >;
                };

     gpio_buttons: gpio_buttons@0 {
               compatible = "gpio-keys";
                 pinctrl-names = "default";
                pinctrl-0 = <&gpio_keys_s0>;
                #address-cells = <1>;
                #size-cells = <0>;

                switch@1 {
                        label = "key_init";
                        debounce_interval = <50>;
                        linux,code = <100>;
                        gpios = <&gpio0 27 GPIO_ACTIVE_HIGH>;
                         gpio-key,wakeup;
                };

                switch@2 {
                        label = "Alaram_key";
                        linux,code = <0x102>;
                        gpios = <&gpio0 22 GPIO_ACTIVE_HIGH>;
                };

                switch@3 {
                        label = "Cancel_key";
                        linux,code = <0x103>;
                        gpios = <&gpio0 26 GPIO_ACTIVE_HIGH>;
                        gpio-key,wakeup;
                };

                switch@4 {
                        label = "Away_key";
                        linux,code = <0x108>;
                        gpios = <&gpio0 23 GPIO_ACTIVE_HIGH>;
                };
        };

I can see the the events occur in /dev/input/event0.

root@am335x-evm:/dev/input# cat event1
▒Dm8▒R
     ▒Dm8▒R
           ▒Dm8'S
                 ▒Dm8'S
                       ▒Dm8=

The problem is I need to read the value and not trigger off of an interrupt. but i want read the value through sys file like leds output root@am335x-evm:/sys/class/leds/beaglebone:green:usr3#
root@am335x-evm:/sys/class/leds/beaglebone:green:usr3# echo 1 >brightness

root@am335x-evm:/sys/class/leds/beaglebone:green:usr3# cat brightness
1

please help me how to read input gpio data as we as how to export gpio buttons attributes to sys directory

Thankas & Regards

shankar

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

I will ask the SW team to look at this.

0 shankar naragoni over 9 years ago in reply to Biser Gatchev-XID

Intellectual 885 points

thank you for your reply.......

0 Kemal R. Shakir over 9 years ago in reply to shankar naragoni

TI__Guru 55345 points

Hello Shankar,

These are the steps for exporting gpio buttons attributes to sys directory.

First you have to release the button's GPIO from the device tree if it is in use from another driver.

Then go to /sys/class/gpio and export it.

For example:

# echo 67 > export
# cd gpio67
# cat value
#0
# cat value
#1

If the button is pressed the value is 1.

Please refer to this link for more detailed information: http://processors.wiki.ti.com/index.php/Linux_PSP_GPIO_Driver_Guide

Best regards,
Kemal

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How GPIO input buttons read through sys file and updating in Device tree in SDK 7(3.12)