DM388: Using GPIOs in DM388 from application(user space)( (IPNC RDK 3.9.0)

Nithin Dominic said:

So we cannot call u-boot function from user application part? Can't we achieve this by including header files with proper makefile for that?

No, you can not use u-boot.

As Dwarakesh states, you should use GPIO sysfs for user space access. See below wiki pages for more info:

http://processors.wiki.ti.com/index.php/Processor_SDK_Linux_GPIO_Driver_Overview

http://processors.wiki.ti.com/index.php/Linux_PSP_GPIO_Driver_Guide

Regards,
Pavel

Thank you Dwarakesh and Pavel,

I was going through the documents and tried as mentioned by Dwarakesh " Export the GPIO(to which LED is connected) to the user space using sysfs and then write the code to access this sysfs entry."

to export the GPIO pin to glow led;

$ echo 56 > /sys/class/gpio/export

$ echo "out" > /sys/class/gpio/gpio56/direction

$ echo 1 > /sys/class/gpio/gpio56/value

Here the LED turns ON.

Then you have mentioned "write the code to access this sysfs entry", where I should write the code? Please explain

How to write the LED glow code anywhere In the code as required?

Regards.

Thank you Pavel,

From following link,

http://processors.wiki.ti.com/index.php/Linux_PSP_GPIO_Driver_Guide#User_Space_-_Sysfs_control

In Driver Usage/ Kernel Level..

I can add the following code in user space:

err = gpio_request(56, LED2);

gpio_direction_output(56, 1);

gpio_export(56, true);

As mentioned in:

please tell me which header file i have to include in my GPIO APIs applications. - Processors forum ...

e2e.ti.com

Other Parts Discussed in Thread: AM1808 , OMAPL138 Hi, I used gpio uaer APIs, writen this below code its getting error what is the problem which header file

I was getting similar errors, here the posts suggest to make changes in the makefile 
to get rid of the errors. But I got a confusion to make changes in:

../ti/ipnc_rdk-3.9.0/Source/ti_tools/ipnc_psp_arago/kernel/drivers/gpio/Makefile

or the place where I'm trying to use  GPIO funtion

../ti/ipnc_rdk-3.9.0/Source/ipnc_rdk/ipnc_app/network/dhcpcd/Makefile

Nithin Dominic said:

../ti/ipnc_rdk-3.9.0/Source/ti_tools/ipnc_psp_arago/kernel/drivers/gpio/Makefile

Nithin Dominic said:

../ti/ipnc_rdk-3.9.0/Source/ipnc_rdk/ipnc_app/network/dhcpcd/Makefile

None of both. You can not use C application with these functions (gpio_request(), gpio_direction_output(), gpio_export()), you should use external kernel module (.ko file) which should be loaded (with insmod/modprobe) from user space.

You should create your own directory (gpio test directory), where you should place your C code (structured as kernel module, not as user space application) and create your own Makefile, fill it and place it in that directory.

Regards,
Pavel

Nithin Dominic said:

So you are saying I cannot call the functions in:

/ti/ipnc_rdk-3.9.0/Source/ti_tools/ipnc_psp_arago/kernel/drivers/gpio/gpiolib-sysfs.c
where we have;
gpiod_export(struct gpio_desc *desc, bool direction_may_change), etc

into my application?

Yes

You can also use C application, but you should export the GPIO functions to user space. All this explained in details in my previous replies.

Nithin Dominic said:

So I should use external kernel module loaded from user space

Yes

Nithin Dominic said:

How can I create .ko files

There is nothing TI specific in this. You might search in google how to create and use external kernel modules. Example tutorial you can find in the below link:

Nithin Dominic said:

To access GPIO pins, I should develop a new GPIO C code?
Where I should place the code, in kernel?

Is it possible to call gpio function into application if I write desperate GPIO code?

I am not able to understand these question, hence I can not provide answers.

Regards,
Pavel

Thank you Pavel,

Now, I'm trying to use C application to access sys/class/gpio from user space.

Let me make the steps to be followed clear;

•    I must use a similar C code available here: 'https://e2e.ti.com/support/embedded/linux/f/354/t/495550'  to access sys/class/gpio from user space
•    Place the code in User Space? or in kernel ? and I can access the GPIOs.
•    So if I'm able to access the gpios from user space what are the APIs or something to set the GPIO pin direction and value (like gpiod_direction_output( ,etc..))?

Can I use the same C code mentioned in the above post, it contains a while(1), I can modify that and use the same for my purpose?

Please help with the proper steps and clear my doubts.

Regards