Hi
I've been wanting to write an SPI skeleton driver to learn the basics. I'm
hoping a driver guru could offer some guidance.
The idea is to write a skeleton driver that simply prints the chip id
Kernel: stock standard mainline 3.16.0-rc7 kernel on Olimex A20-SOM (EVK)
Device: MPU9250 Break out board
My thinking so far:
1. DTS
Add an SPI slave device to my DTS file.
I will connect the Break out board to the second SPI bus .... so need to
add the slave device to SPI1
Existing SPI1 device (from dts file)
spi1: spi@01c06000 {
pinctrl-names = "default";
pinctrl-0 = <&spi1_pins_a>;
status = "okay";
};
Adding SPI1 slave device:
spi1: spi@01c06000 {
pinctrl-names = "default";
pinctrl-0 = <&spi1_pins_a>;
status = "okay";
mpu9250@0 {
compatible = "mpu9250";
reg = <0>;
spi-max-frequency = <1000000>;
???? interrupt pin .... gpio ???????
};
};
2. The driver will create an entry in "sysfs" and a "corresponding" entry
in /dev. Catting the device " /dev/mpu9250 " will return the device id.
Then the driver will be a standard Linux kernel module with support for SPI
....
#include <linux/module.h>
#include <linux/spi/spi.h>
....
struct spi_driver
spi_register_driver (struct device dev; dictates the name of the device)
spi_alloc_device
spi_add_device
Am I on the right track? Any similar simple examples floating about?
Thanks
Bruce
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