com.diozero.internal.spi.SpiDeviceFactoryInterface Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of diozero-core Show documentation
There is a newer version: 1.4.1
package com.diozero.internal.spi;

/*
 * #%L
 * Organisation: diozero
 * Project:      Device I/O Zero - Core
 * Filename:     SpiDeviceFactoryInterface.java  
 * 
 * This file is part of the diozero project. More information about this project
 * can be found at http://www.diozero.com/
 * %%
 * Copyright (C) 2016 - 2021 diozero
 * %%
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * #L%
 */


import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

import org.tinylog.Logger;

import com.diozero.api.DeviceAlreadyOpenedException;
import com.diozero.api.RuntimeIOException;
import com.diozero.api.SpiClockMode;
import com.diozero.api.SpiDeviceInterface;

public interface SpiDeviceFactoryInterface extends DeviceFactoryInterface {
	/**
	 * Many distributions have a maximum SPI transfer of 4096 bytes. This can be changed in /boot/cmdline.txt by appending
	 *  spidev.bufsiz=32768
 	 */
	static final int DEFAULT_SPI_BUFFER_SIZE = 4096;
	static final String SPI_PREFIX = "-SPI-";
	
	default SpiDeviceInterface provisionSpiDevice(int controller, int chipSelect,
			int frequency, SpiClockMode spiClockMode, boolean lsbFirst) throws RuntimeIOException {
		String key = createSpiKey(controller, chipSelect);
		
		// Check if this pin is already provisioned
		if (isDeviceOpened(key)) {
			throw new DeviceAlreadyOpenedException("Device " + key + " is already in use");
		}
		
		SpiDeviceInterface device = createSpiDevice(key, controller, chipSelect, frequency, spiClockMode, lsbFirst);
		deviceOpened(device);
		
		return device;
	}

	SpiDeviceInterface createSpiDevice(String key, int controller, int chipSelect, int frequency,
			SpiClockMode spiClockMode, boolean lsbFirst) throws RuntimeIOException;

	default int getSpiBufferSize() {
		try {
			return Files.lines(Paths.get("/sys/module/spidev/parameters/bufsiz")).mapToInt(Integer::parseInt).findFirst()
					.orElse(DEFAULT_SPI_BUFFER_SIZE);
		} catch (IOException e) {
			Logger.warn("Unable to read kernel SPI buffer size, using default: {}", e);
			return DEFAULT_SPI_BUFFER_SIZE;
		}
	}
	
	static String createSpiKey(String keyPrefix, int controller, int chipSelect) {
		return keyPrefix + SPI_PREFIX + controller + "-" + chipSelect;
	}
}