Add an LED driver example using GPIO #290
Conversation
jeremy90307
force-pushed
the
master
branch
3 times, most recently
from
3a799e4 to
a64cd81
Compare
examples/led.c
Outdated
| { | ||
| pr_info("device_open(%p)\n", file); | ||
|
|
||
| try_module_get(THIS_MODULE); |
There was a problem hiding this comment.
See if try_module_get is required or not.
There was a problem hiding this comment.
I have noticed this issue, such as issue #52, and there are still several examples using it. Let me fix it.
There was a problem hiding this comment.
If we want to remove try_module_get, we also need to stop using register_chrdev and use cdev_init and cdev_add instead.
Because with register_chrdev, we need to manually increase or decrease the module's reference count.
There was a problem hiding this comment.
The try_module_get() function should generally be avoided. The only legitimate use case is when you need to reference another module before interacting with it, such as in file operations code. While try_module_get(THIS_MODULE) appears multiple times in the kernel source code, these instances are typically bugs that need to be fixed rather than examples to follow.
There was a problem hiding this comment.
In my modified code, register_chrdev is not included. Should I use the preprocessor to make the changes?
There was a problem hiding this comment.
Because I saw that cdev already appeared in Linux v2.6.
jeremy90307
force-pushed
the
master
branch
2 times, most recently
from
998113c to
9c56420
Compare
lkmpg.tex
Outdated
| Therefore, we will further use Device Files to control the LED on and off. | ||
|
|
||
| In the implementation, a pull-down resistor is used. | ||
| The positive electrode of the LED is connected to GPIO4, and the negative electrode is connected to GND. |
There was a problem hiding this comment.
Can you provide some hyperlinks which illustrate the GPIO assignments?
Use GPIO to control LED on/off and add related GPIO knowledge. Test detail: - Tested on Raspberry Pi 5B with Raspberry Pi OS (Debian 12, Linux version 6.12.1-v8-16k+) - Verify that LED example compiles and loads successfully - Verify that LED turns on and off sucessfully
|
Thank @jeremy90307 for contributing! |
Add an LED driver example using GPIO and add related knowledge.
Test detail:
Tested on Raspberry Pi 5B with Raspberry Pi OS (Debian 12, Linux version 6.12.1-v8-16k+)
Verify that LED sample compiles and loads successfully
Verify that LED turns on and off sucessfully
Summary by Bito
This pull request introduces a new LED driver example for the Raspberry Pi 5B, featuring a new source file 'led.c' for GPIO control. The Makefile has been updated accordingly, and comprehensive documentation on GPIO and LED control has been added to 'lkmpg.tex'. The implementation has been successfully tested on the Raspberry Pi 5B.Unit tests added: False
Estimated effort to review (1-5, lower is better): 2