This email is basically a request for opinions on how and where such sensors should be integrated into the kernel. To set the scene... Increasing numbers of embedded devices are being supplied attached MEMS devices (www.xbow.com imote2 etc). Along with more traditional sensors such as ADC's not being used for hardware monitoring, these do not really seem to fit with in an particular subsystem of the kernel. A previous discussion on lkml in 2006 considered the accelerometers to be found within some laptop hard drives, but I haven't been able to track down any more general discussions of such non hardware monitoring sensors. The obvious possibilities are: * To place the various drivers within the spi / i2c etc subsystems as relevant. * To place within the hwmon subsystem as this is probably closest. (there is already at least one straight ADC driver in hwmon) * To create a new subsystem, or perhaps merely sysfs class to contain these elements. Typical requirements within an application include simply polling for current readings, and using device triggered interrupts to grab data continuously to a ring buffer, for collection by suitable userspace code. Obviously it would be desirable to standardize sysfs controls for various calibration parameters as much as possible across the various devices. Any other suggestions welcome! To illustrate the sort of devices here are a few I have drivers written for or will shortly be writing (some submitted to hwmon and spi mailing lists, some not finished as of yet) ST Micro LIS3L02DQ 3D accelerometer. SPI device, no buffering, interrupt pin raised high on new data being available. Currently the driver assumes, if interrupts are enabled, that this is connected to a specified gpio. (http://www.st.com/stonline/books/pdf/docs/10175.pdf) VTI SCA3000 E05 3D accelerometer equiped with substantial ring buffer. SPI device. Can operate either in buffered or direct mode. In buffered mode, interrupts can be used to indicate when the ring buffer is 3/4 full triggering a download to a larger ring buffer in the kernel if necessary. (http://www.vti.fi/en/products-solutions/products/accelerometers/sca3000-accelerometers/) Analog Devices ADIS16350 combined 3D accelerometer and gyro unit. SPI device. (http://www.analog.com/en/prod/0,,764_801_ADIS16350%2C00.html) Maxim MAX1363, MAX1238 ADC's. I2C devices. Some SPI ADC's (www.analog.com for examples) Would be nice if practical to allow the framework to include RS232 devices such as those from www.xsens.com, www.isense.com and others. -- Jonathan Cameron
