Introduction to Android G Sensor I²C Driver on Android
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This document provides an introduction and overview of G sensor I2C drivers on Android. It discusses what a G sensor is and its applications. It then covers the key aspects of implementing an I2C driver for a G sensor from initializing the driver and registering it, to detecting and probing devices, and creating I2C clients. Issues that may occur and how to resolve them are also addressed.
![I2c Driver: i2c_detect /* initial i2c client structure */ struct i2c_client *temp_client; temp_client->adapter = adapter; /* get address from i2c_client_address_data*/ address_data = driver ->address_data; /* check if Legacy driver */ if (! driver ->detect || ! address_data ) /* check normal_i2c ignore probe address */ for(i = 0; address_data ->normal_i2c[i] != I2C_CLIENT_END ; i += 1)](https://image.slidesharecdn.com/introductiontogsensori2cdriver-100606220735-phpapp01/85/Introduction-to-Android-G-Sensor-I-C-Driver-on-Android-16-320.jpg)
![I2c Driver: i2c_detect_address /* Make sure the address is valid */ ( addr < 0x03 || addr > 0x77 ) /* Make sure there is something at this address */ i2c_smbus_xfer (adapter, addr, 0, 0, 0, I2C_SMBUS_QUICK , NULL) /* Finally call the custom detection function */ memset(&info, 0, sizeof(struct i2c_board_info)); driver-> detect (temp_client, kind, &info); use info.type[0] == '\0‘ to check driver->detect function /* Detection succeeded, instantiate the device */ client = i2c_new_device (adapter, &info); list_add_tail (&client->detected, &driver->clients);](https://image.slidesharecdn.com/introductiontogsensori2cdriver-100606220735-phpapp01/85/Introduction-to-Android-G-Sensor-I-C-Driver-on-Android-17-320.jpg)
Introduction to Android G Sensor I²C Driver on Android
- 1. Introduction to Android G sensor I²C Driver on Android Bo-Yi Wu 2010.06.04 Gemtek Technology Co., Ltd
- 2. Outline What’s G sensor ? I²C Driver Kernel Patch Issue Reference
- 3. What’s G sensor & Application As accelerometers are more and more present in mobile devices, new features are developed. Portrait & Landscape is one of them. It allows devices to display the information in the right orientation depending on how it is held.
- 6. Stability check STABLE_THRES STABLE_COUNT_MIN calling rate? bigger or smaller?
- 7. Code Review
- 8. I²C : detection capability set i2c address value detect call back function detect address fill the structure i2c_board_info
- 9. New-style drivers vs Legacy drivers Legacy drivers duplicate a lot of code . The code needed in each driver to implement a detect callback is way smaller than the code needed to implement a legacy driver.
- 10. New-style drivers: initial function module_init ( BMA150_init ); return i2c_add_driver (&bma150_driver); module_exit ( BMA150_exit ); i2c_del_driver (&bma150_driver); __exit && __init (Kernel built in or module)
- 11. G Sensor: bma150_driver structure New-style driver Legacy driver probe: Callback for device binding (new-style drivers) remove: Callback for device unbinding (new-style drivers) class : What kind of i2c device we instantiate (for detect) (1<<0) for sensor address_data: The I2C addresses to probe, ignore or force (for detect) id_table: List of I2C devices supported by this driver
- 13. New-style drivers: address_data /* Internal numbers to terminate lists */ I2C_CLIENT_END : 0xfffeU I2C_CLIENT_INSMOD_1 ~ I2C_CLIENT_INSMOD_8 I2C_CLIENT_INSMOD_COMMON : define structure address_data normal_i2c, probe, ignore value
- 14. I2c Driver: i2c_register_driver 1. new style driver methods can't mix with legacy ones /* check bma150_driver is news style driver or not */ is_newstyle_driver (driver) 2. /* check bma150_driver is Legacy style driver or not */ driver->attach_adapter || driver->detach_adapter || driver->detach_client 4. /* add bma150 driver to list for i2c only */ INIT_LIST_HEAD (&driver->clients) 5. /* Walk the adapters that are already present */ class_for_each_device struct i2c_adapter *adapter = to_i2c_adapter(dev); struct i2c_driver *driver = data; 3. /* register driver with bus, and use bus_add_driver () to add bus driver */ driver_register (&driver->driver);
- 15. I2c Driver: __attach_adapter Call __attach_adapter function New style driver: i2c_detect (adapter, driver); Legacy driver: driver-> attach_adapter (adapter); /* Because Legacy driver don’t have detect function */ if (!driver-> detect || !address_data) return 0;
- 16. I2c Driver: i2c_detect /* initial i2c client structure */ struct i2c_client *temp_client; temp_client->adapter = adapter; /* get address from i2c_client_address_data*/ address_data = driver ->address_data; /* check if Legacy driver */ if (! driver ->detect || ! address_data ) /* check normal_i2c ignore probe address */ for(i = 0; address_data ->normal_i2c[i] != I2C_CLIENT_END ; i += 1)
- 17. I2c Driver: i2c_detect_address /* Make sure the address is valid */ ( addr < 0x03 || addr > 0x77 ) /* Make sure there is something at this address */ i2c_smbus_xfer (adapter, addr, 0, 0, 0, I2C_SMBUS_QUICK , NULL) /* Finally call the custom detection function */ memset(&info, 0, sizeof(struct i2c_board_info)); driver-> detect (temp_client, kind, &info); use info.type[0] == '\0‘ to check driver->detect function /* Detection succeeded, instantiate the device */ client = i2c_new_device (adapter, &info); list_add_tail (&client->detected, &driver->clients);
- 18. I2c Driver: i2c_new_device Set i2c_client info from i2c_board_info structure strlcpy (client->name, info->type, sizeof(client->name)); client->addr = info->addr; client->irq = info->irq; ……… ..
- 19. I2c Driver: i2c_device_match I2c_bus_type is used on new-style driver i2c_device_match match client i2c_device_id table && i2c_client table id i2c_device_probe Call bma150_probe function if you defined driver’s probe.
- 20. I2c Driver:bma150_probe /* bma150 device create ok if return 0*/ misc_register (&bma_device); /* initial data */ data->smb380. bus_write = bma150_i2c_write; data->smb380. bus_read = bma150_i2c_read; data->smb380. delay_msec = bma150_i2c_delay; data->smb380. dev_addr = client->addr; smb380_init(&(data->smb380));
- 22. Build Linux Kernel Edit Kconfig & Makefile Patch all files(bma150_drivers.c…) Make menuconfig Make uImage
- 23. Issue: can’t create device /* Make sure there is something at this address */ i2c_smbus_xfer (adapter, addr, 0, 0, 0, I2C_SMBUS_QUICK , NULL) Please edit i2c_smbus_xfer_emulated function and Change message data length: 0 -> 1
- 24. Demo To Do: jni module
- 25. Reference Linux Device Drivers, Third Edition
- 26. Thank You.