Difference between revisions of "IMX LED Driver TP"

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== Howto Load/unload modules : "hwmon" module ==
 
== Howto Load/unload modules : "hwmon" module ==
−
Load module is quite simple once it is compile an in the rootfs of the apf board.
+
Loading a module is quite simple once it is compiled and is present in the rootfs of the apf board.
−
All the compiled driver modules are in the "/lib/modules/<kernel version>/kernel". To find all the loadable modules by the kernel in the board type :
+
All the compiled driver modules are in the "/lib/modules/<kernel version>/kernel" in the apf rootfs. To list all the loadable modules by the kernel in the board type :
 
<pre class="apf">
 
<pre class="apf">
 
  # find /lib/modules/`uname -r`/kernel -name "*.ko"
 
  # find /lib/modules/`uname -r`/kernel -name "*.ko"
Line 29: Line 29:
 
  #
 
  #
 
</pre>
 
</pre>
 +
To list all mod loaded :
 +
<pre class="apf">
 +
# lsmod
 +
Module                  Size  Used by    Not tainted
 +
hwmon                  2356  0
 +
</pre>
 +
 
To unload it just type :
 
To unload it just type :
 
<pre class="apf">
 
<pre class="apf">
Line 36: Line 43:
 
TBC
 
TBC
  
−
== Howto Build a simple module and load/unload it : the "Hello World" module ==
+
== Howto Build a simple char module and load/unload it : the "Hello World" module ==
 +
The "Hello World" module code is quite simple have only load and unload fonction.
 +
=== Create required folder and files ===
 +
Create a hello folder in <armadeus_directory>/target/linux/modules/. On the host computer type :
  
 +
<pre class="host">
 +
cd <armadeus_directory>/target/linux/modules/
 +
mkdir hello
 +
</pre>
 +
==== Hello.c source file ====
 +
<source lang="c">
 +
#include <linux/module.h> /* Default module librairies TBC */
 +
#include <linux/kernel.h>
 +
 +
/* Print "Hello, world\n" with KERN_ALERT level (stdio TBC) */
 +
static int hello_init(void){
 +
      printk(KERN_ALERT "Hello, world\n");
 +
      return 0;
 +
}
 +
 +
/* Print "Goodbye, cruel world\n" with KERN_ALERT level (stdio TBC) */
 +
static void hello_exit(void){
 +
      printk(KERN_ALERT "Goodbye, cruel world\n");
 +
}
 +
 +
module_init(hello_init); /* Set hello_init function as the module init one (called when module load) */
 +
module_exit(hello_exit); /* Set hello_exit function as the module exit one (called when module unload) */
 +
 +
MODULE_LICENSE("GPL"); /* Set the license module */
 +
</source>
 +
==== Makefile file ====
 +
<source lang="text">
 +
# Part executed when called from kernel build system:
 +
ifneq ($(KERNELRELEASE),)
 +
 +
obj-$(CONFIG_ARMADEUS_LED_XAV_DRIVER) += hello.o
 +
 +
#hello-objs := hello.o
 +
 +
# Part executed when called from standard make in this directory:
 +
# (preferably use Makefile in parent directory)
 +
else
 +
 +
ARMADEUS_BASE_DIR=../../../..
 +
include $(ARMADEUS_BASE_DIR)/Makefile.in
 +
 +
KDIR    := $(ARMADEUS_LINUX_DIR)
 +
PWD := $(shell pwd)
 +
 +
# Armadeus custom drivers common targets:
 +
include ../Makefile.in
 +
 +
endif
 +
</source>
 +
TBC
 
== Howto Provide read/write commands to the user though /dev/hello : "Hello World Read Write" module ==
 
== Howto Provide read/write commands to the user though /dev/hello : "Hello World Read Write" module ==
  
 
== Howto Build a register use module : "iMX LED" module ==
 
== Howto Build a register use module : "iMX LED" module ==

Latest revision as of 19:57, 30 March 2009

Page under construction... Construction.png Informations on this page are not guaranteed !!

Proposal

The goal of this tutorial is to build from scratch a simple led driver wire on GPIO of the iMX. This document will describes step by step how to implement a such driver

Howto Load/unload modules : "hwmon" module

Loading a module is quite simple once it is compiled and is present in the rootfs of the apf board. All the compiled driver modules are in the "/lib/modules/<kernel version>/kernel" in the apf rootfs. To list all the loadable modules by the kernel in the board type : 

 # find /lib/modules/`uname -r`/kernel -name "*.ko"
/lib/modules/2.6.27.13/kernel/sound/arm/snd-imx-alsa-tsc2102.ko
/lib/modules/2.6.27.13/kernel/sound/arm/snd-mx2.ko
/lib/modules/2.6.27.13/kernel/sound/core/snd-page-alloc.ko
/lib/modules/2.6.27.13/kernel/sound/core/snd-timer.ko
/lib/modules/2.6.27.13/kernel/sound/core/snd.ko
/lib/modules/2.6.27.13/kernel/sound/core/snd-pcm.ko
/lib/modules/2.6.27.13/kernel/sound/soundcore.ko
/lib/modules/2.6.27.13/kernel/drivers/spi/tsc2102.ko
/lib/modules/2.6.27.13/kernel/drivers/scsi/scsi_wait_scan.ko
/lib/modules/2.6.27.13/kernel/drivers/hwmon/hwmon.ko
/lib/modules/2.6.27.13/kernel/drivers/input/touchscreen/tsc2102_ts.ko
/lib/modules/2.6.27.13/kernel/drivers/video/backlight/lcd.ko
/lib/modules/2.6.27.13/kernel/drivers/video/backlight/backlight.ko
/lib/modules/2.6.27.13/kernel/drivers/armadeus/max1027/max1027.ko
/lib/modules/2.6.27.13/kernel/drivers/armadeus/backlight/imx_bl.ko

For example, I will load "/lib/modules/2.6.27.13/kernel/drivers/hwmon/hwmon.ko" module : 

 # modprobe hwmon
 #

To list all mod loaded : 

 # lsmod
Module                  Size  Used by    Not tainted
hwmon                   2356  0

To unload it just type : 

 # rmmod hwmon
 #

TBC

Howto Build a simple char module and load/unload it : the "Hello World" module

The "Hello World" module code is quite simple have only load and unload fonction.

Create required folder and files

Create a hello folder in <armadeus_directory>/target/linux/modules/. On the host computer type : 

cd <armadeus_directory>/target/linux/modules/
mkdir hello

Hello.c source file

#include <linux/module.h> /* Default module librairies TBC */
#include <linux/kernel.h>

/* Print "Hello, world\n" with KERN_ALERT level (stdio TBC) */
static int hello_init(void){
      printk(KERN_ALERT "Hello, world\n");
      return 0;
}

/* Print "Goodbye, cruel world\n" with KERN_ALERT level (stdio TBC) */
static void hello_exit(void){
      printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init); /* Set hello_init function as the module init one (called when module load) */
module_exit(hello_exit); /* Set hello_exit function as the module exit one (called when module unload) */

MODULE_LICENSE("GPL"); /* Set the license module */

Makefile file

# Part executed when called from kernel build system:
ifneq ($(KERNELRELEASE),)

obj-$(CONFIG_ARMADEUS_LED_XAV_DRIVER)	+= hello.o

#hello-objs	:= hello.o

# Part executed when called from standard make in this directory:
# (preferably use Makefile in parent directory)
else

ARMADEUS_BASE_DIR=../../../..
include $(ARMADEUS_BASE_DIR)/Makefile.in

KDIR    := $(ARMADEUS_LINUX_DIR)
PWD	:= $(shell pwd)

# Armadeus custom drivers common targets:
include ../Makefile.in

endif

TBC

Howto Provide read/write commands to the user though /dev/hello : "Hello World Read Write" module

Howto Build a register use module : "iMX LED" module

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