Linux kernel space

AN4503

12/26

DocID026411 Rev 2

3

Linux kernel space

This layer contains the Linux device drivers: hts221.ko, lps25.ko and uv.ko.

They use the input subsystem, which is a generic Linux framework that is common for other

input devices including mouse and joystick. The data is exported to the user space through

the Sysfs virtual file system (/sys/class/input/) and can be found in /dev/input/input<x>,

where <x> is unique for every device. The driver sends/receives data to/from the sensor

through the stable Linux subsystem I²C.

Note:

At the time of writing, the hts221 driver only functions in OneShot mode.

3.1

Overview of the environment

To properly configure the PandaBoard, the adapters for humidity, pressure and ultraviolet

are connected to the PandaBoard on the I²C bus (refer to Chapter 4.1)

The file board-omap4panda.c in [KR]/arch/arm/mach-omap2/board-omap4panda.c is then

patched as described below.

3.1.1

I²C bus initialization patch

static int __init omap4_panda_i2c_init(void)

{

omap4_pmic_init("twl6030", &omap4_panda_twldata);

omap_register_i2c_bus(2, 400, NULL, 0);

/*

* Bus 3 is attached to the DVI port where devices like the pico DLP

* projector don't work reliably with 400kHz

*/

omap_register_i2c_bus(3, 100, panda_i2c_eeprom,

ARRAY_SIZE(panda_i2c_eeprom));

omap_register_i2c_bus(4, 200, panda_i2c_memsensors,

ARRAY_SIZE(panda_i2c_memsensors)

);

return 0;

}

Initialize bus 4 (which the devices are connected to) by adding the above line in bold.

The structures below are also added.