#454 Add first SPI implementation, tests (with native mock driver) and minor refactoring

Author: DigitalSmile

plugins/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/FFMPlugin.java

@@ -8,7 +8,7 @@
 import com.pi4j.plugin.ffm.providers.gpio.DigitalOutputFFMProviderImpl;
 import com.pi4j.plugin.ffm.providers.i2c.I2CFFMProviderImpl;
 import com.pi4j.plugin.ffm.providers.pwm.FFMPwmProviderImpl;
-import com.pi4j.plugin.ffm.providers.spi.FFMSpiProviderImpl;
+import com.pi4j.plugin.ffm.providers.spi.SpiFFMProviderImpl;
 import com.pi4j.provider.Provider;
 
 import java.util.Arrays;
@@ -22,7 +22,7 @@ public void initialize(PluginService service) {
           new DigitalInputFFMProviderImpl(),
           new DigitalOutputFFMProviderImpl(),
           new I2CFFMProviderImpl(),
-          new FFMSpiProviderImpl(),
+          new SpiFFMProviderImpl(),
           new FFMPwmProviderImpl()
         };
         service.register(providers);

plugins/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/common/ioctl/Command.java

@@ -15,6 +15,9 @@ public static long getGpioGetChipInfoIoctl() {
         return IoctlMagic.GPIO_GET_CHIPINFO_IOCTL;
     }
 
+    public static long getSpiIocMessage(int n) {
+        return IoctlMagic.SPI_IOC_MESSAGE(n);
+    }
 
     public static long getSpiIocRdMode() {
         return IoctlMagic.SPI_IOC_RD_MODE;

plugins/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/common/ioctl/IoctlMagic.java

@@ -89,7 +89,7 @@ static int SPI_MSGSIZE(int N) {
 
     static int SPI_IOC_TRANSFER_SIZE() {
         if (_SPI_IOC_TRANSFER_SIZE == -1) {
-            _SPI_IOC_TRANSFER_SIZE = 44;
+            _SPI_IOC_TRANSFER_SIZE = 32;
         }
         return _SPI_IOC_TRANSFER_SIZE;
     }

plugins/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/common/spi/SpiIocTransfer.java

@@ -0,0 +1,128 @@
+package com.pi4j.plugin.ffm.common.spi;
+
+import com.pi4j.plugin.ffm.common.Pi4JLayout;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemoryLayout;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.VarHandle;
+import java.util.Arrays;
+
+import static java.lang.foreign.MemoryLayout.PathElement.groupElement;
+
+/**
+ * Source: /usr/src/linux-headers-6.8.0-52-generic/include/linux/spi/spidev.h:70:0
+ */
+public record SpiIocTransfer(byte[] txBuf, byte[] rxBuf, int length, int speedHz, short delayUsecs, byte bitsPerWord,
+                             byte csChange, byte txNbits, byte rxNbits, byte wordDelayUsecs,
+                             byte pad) implements Pi4JLayout {
+
+    public SpiIocTransfer(byte[] txBuf, byte[] rxBuf, int length) {
+        this(txBuf, rxBuf, length, 0, (short) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0);
+    }
+
+    public static final MemoryLayout LAYOUT = MemoryLayout.structLayout(
+        ValueLayout.JAVA_LONG.withName("tx_buf"),
+        ValueLayout.JAVA_LONG.withName("rx_buf"),
+        ValueLayout.JAVA_INT.withName("len"),
+        ValueLayout.JAVA_INT.withName("speed_hz"),
+        ValueLayout.JAVA_SHORT.withName("delay_usecs"),
+        ValueLayout.JAVA_BYTE.withName("bits_per_word"),
+        ValueLayout.JAVA_BYTE.withName("cs_change"),
+        ValueLayout.JAVA_BYTE.withName("tx_nbits"),
+        ValueLayout.JAVA_BYTE.withName("rx_nbits"),
+        ValueLayout.JAVA_BYTE.withName("word_delay_usecs"),
+        ValueLayout.JAVA_BYTE.withName("pad")
+    );
+
+    private static final VarHandle VH_TX_BUF = LAYOUT.varHandle(groupElement("tx_buf"));
+    private static final VarHandle VH_RX_BUF = LAYOUT.varHandle(groupElement("rx_buf"));
+
+    private static final VarHandle VH_LEN = LAYOUT.varHandle(groupElement("len"));
+    private static final VarHandle VH_SPEED_HZ = LAYOUT.varHandle(groupElement("speed_hz"));
+    private static final VarHandle VH_DELAY_USECS = LAYOUT.varHandle(groupElement("delay_usecs"));
+    private static final VarHandle VH_BITS_PER_WORD = LAYOUT.varHandle(groupElement("bits_per_word"));
+    private static final VarHandle VH_CS_CHANGE = LAYOUT.varHandle(groupElement("cs_change"));
+    private static final VarHandle VH_TX_NBITS = LAYOUT.varHandle(groupElement("tx_nbits"));
+    private static final VarHandle VH_RX_NBITS = LAYOUT.varHandle(groupElement("rx_nbits"));
+    private static final VarHandle VH_WORD_DELAY_USECS = LAYOUT.varHandle(groupElement("word_delay_usecs"));
+    private static final VarHandle VH_PAD = LAYOUT.varHandle(groupElement("pad"));
+
+
+    public static SpiIocTransfer create(MemorySegment memorySegment) throws Throwable {
+        var spiIocTransferInstance = SpiIocTransfer.createEmpty();
+        if (!memorySegment.equals(MemorySegment.NULL)) {
+            spiIocTransferInstance = spiIocTransferInstance.from(memorySegment);
+        }
+        return spiIocTransferInstance;
+    }
+
+    public static SpiIocTransfer createEmpty() {
+        return new SpiIocTransfer(new byte[]{}, new byte[]{}, 0, 0, (short) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0, (byte) 0);
+    }
+
+    @Override
+    public MemoryLayout getMemoryLayout() {
+        return LAYOUT;
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public SpiIocTransfer from(MemorySegment buffer) throws Throwable {
+        return new SpiIocTransfer(
+            txBuf1 != null ? txBuf1.toArray(ValueLayout.JAVA_BYTE) : new byte[]{},
+            rxBuf1 != null ? rxBuf1.toArray(ValueLayout.JAVA_BYTE) : new byte[]{},
+            (int) VH_LEN.get(buffer, 0L),
+            (int) VH_SPEED_HZ.get(buffer, 0L),
+            (short) VH_DELAY_USECS.get(buffer, 0L),
+            (byte) VH_BITS_PER_WORD.get(buffer, 0L),
+            (byte) VH_CS_CHANGE.get(buffer, 0L),
+            (byte) VH_TX_NBITS.get(buffer, 0L),
+            (byte) VH_RX_NBITS.get(buffer, 0L),
+            (byte) VH_WORD_DELAY_USECS.get(buffer, 0L),
+            (byte) VH_PAD.get(buffer, 0L));
+    }
+
+    public static MemorySegment txBuf1;
+    public static MemorySegment rxBuf1;
+
+    @Override
+    public void to(MemorySegment buffer) throws Throwable {
+        if (txBuf != null) {
+            txBuf1 = Arena.global().allocateFrom(ValueLayout.JAVA_BYTE, txBuf);
+            VH_TX_BUF.set(buffer, 0L, txBuf1.address());
+        }
+        if (rxBuf != null) {
+            rxBuf1 = Arena.global().allocateFrom(ValueLayout.JAVA_BYTE, rxBuf);
+            VH_RX_BUF.set(buffer, 0L, rxBuf1.address());
+        }
+        VH_LEN.set(buffer, 0L, length);
+        VH_SPEED_HZ.set(buffer, 0L, speedHz);
+        VH_DELAY_USECS.set(buffer, 0L, delayUsecs);
+        VH_BITS_PER_WORD.set(buffer, 0L, bitsPerWord);
+        VH_CS_CHANGE.set(buffer, 0L, csChange);
+        VH_TX_NBITS.set(buffer, 0L, txNbits);
+        VH_RX_NBITS.set(buffer, 0L, rxNbits);
+        VH_WORD_DELAY_USECS.set(buffer, 0L, wordDelayUsecs);
+        VH_PAD.set(buffer, 0L, pad);
+    }
+
+
+    @Override
+    public String toString() {
+        return "SpiIocTransfer{" +
+            "txBuf=" + Arrays.toString(txBuf) +
+            ", rxBuf=" + Arrays.toString(rxBuf) +
+            ", length=" + length +
+            ", speedHz=" + speedHz +
+            ", delayUsecs=" + delayUsecs +
+            ", bitsPerWord=" + bitsPerWord +
+            ", csChange=" + csChange +
+            ", txNbits=" + txNbits +
+            ", rxNbits=" + rxNbits +
+            ", wordDelayUsecs=" + wordDelayUsecs +
+            ", pad=" + pad +
+            '}';
+    }
+}

plugins/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/providers/i2c/I2CSMBus.java

@@ -127,7 +127,6 @@ public int writeRegister(int register, byte[] data, int offset, int length) {
 
     @Override
     public int writeRegister(byte[] register, byte[] data, int offset, int length) {
-        //TODO: how to implement? That is not a part of standard.
         Objects.checkFromIndexSize(offset, length, data.length);
         // Prepare the data for multibyte register
         // Sequence:
@@ -144,6 +143,5 @@ public int writeRegister(byte[] register, byte[] data, int offset, int length) {
     public void close() {
         super.close();
         i2CBus.close();
-        SMBUS.close();
     }
 }