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#654 Added an initial state to FFMDigitalOutput #663

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Merged
eitch merged 1 commit into from
Jun 19, 2026
Merged

#654 Added an initial state to FFMDigitalOutput #663

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17 changes: 16 additions & 1 deletion ...ns/pi4j-plugin-ffm/src/main/java/com/pi4j/plugin/ffm/providers/gpio/FFMDigitalOutput.java
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
import com.pi4j.plugin.ffm.common.file.FileDescriptorNative;
import com.pi4j.plugin.ffm.common.file.FileFlag;
import com.pi4j.plugin.ffm.common.gpio.PinFlag;
import com.pi4j.plugin.ffm.common.gpio.enums.LineAttributeId;
import com.pi4j.plugin.ffm.common.gpio.structs.*;
import com.pi4j.plugin.ffm.common.ioctl.Command;
import com.pi4j.plugin.ffm.common.ioctl.IoctlNative;
Expand All @@ -20,6 +21,7 @@
import java.nio.file.Path;
import java.nio.file.attribute.PosixFileAttributes;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.ArrayList;

public class FFMDigitalOutput extends DigitalOutputBase implements DigitalOutput {
private static final Logger logger = LoggerFactory.getLogger(FFMDigitalOutput.class);
Expand Down Expand Up @@ -59,7 +61,20 @@ public DigitalOutput initialize(Context context) throws InitializeException {
}
logger.trace("{}-{} - DigitalOutput BCM line info: {}", deviceName, bcm, lineInfo);
var flags = PinFlag.OUTPUT.getValue();
var lineConfig = new LineConfig(flags, 0, new LineConfigAttribute[]{});
var attributes = new ArrayList<LineConfigAttribute>();
var initialState = config().initialState();
if (initialState != null) {
// Pass the configured initial state to the kernel as part of the line request so the
// pin is driven to it the moment the line is requested. Without this the kernel drives
// a newly requested output low by default and the pin is only switched to the initial
// state afterwards, producing a transient low-then-high glitch (issue #654).
var values = initialState.isHigh() ? 1L : 0L;
var outputValues = new LineAttribute(LineAttributeId.GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES.getValue(), 0, values, 0);
// The single requested line lives at index 0 of the offsets array, so its mask bit is 0.
attributes.add(new LineConfigAttribute(outputValues, 1L));
logger.trace("{}-{} - DigitalOutput BCM initial state: {}", deviceName, bcm, initialState);
}
var lineConfig = new LineConfig(flags, attributes.size(), attributes.toArray(new LineConfigAttribute[0]));
var lineRequest = new LineRequest(new int[]{bcm}, ("pi4j." + getClass().getSimpleName()).getBytes(), lineConfig, 1, 0, 0);
var result = ioctl.call(fd, Command.getGpioV2GetLineIoctl(), lineRequest);
this.chipFileDescriptor = result.fd();
Expand Down
18 changes: 18 additions & 0 deletions plugins/pi4j-plugin-ffm/src/test/java/com/pi4j/plugin/ffm/integration/GPIOTest.java
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Expand Up @@ -153,4 +153,22 @@ public void testOutputCustomConfig() {
assertEquals(DigitalState.HIGH, output.config().initialState());
assertEquals(6, output.bcm());
}


@Test
public void testOutputInitialStateHigh() {
// Requesting an output with initial state HIGH must succeed through the real character
// device ABI: the kernel validates the output-values attribute we attach to the line
// request and rejects a malformed one with EINVAL. A successful creation therefore proves
// the initial state is passed to the kernel at request time (issue #654).
var config = DigitalOutputConfigBuilder.newInstance()
.bus(97)
.bcm(7)
.initial(DigitalState.HIGH)
.build();
var output = pi4j0.digitalOutput().create(config);
assertEquals(7, output.bcm());
assertEquals(DigitalState.HIGH, output.config().initialState());
assertEquals(DigitalState.HIGH, output.state());
}
}
8 changes: 5 additions & 3 deletions plugins/pi4j-plugin-ffm/src/test/java/com/pi4j/plugin/ffm/mocks/IoctlNativeMock.java
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Expand Up @@ -21,14 +21,16 @@ public record IoctlTestData(Class<? extends Pi4JLayout> objClass, Function<Invoc

public static MockedConstruction<IoctlNative> setup(IoctlTestData... data) {
return mockConstruction(IoctlNative.class, (mock, _) -> {
for (IoctlTestData testData : data) {
when(mock.call(anyInt(), anyLong(), isA(testData.objClass))).thenAnswer(testData.callback::apply);
}
// Register the defaults first so that test-provided callbacks for the same struct
// (e.g. LineRequest) take precedence over them.
when(mock.call(anyInt(), anyLong(), isA(LineValues.class))).thenAnswer((answer) -> answer.<LineValues>getArgument(2));
when(mock.call(anyInt(), anyLong(), isA(LineRequest.class))).thenAnswer((answer) -> {
LineRequest lineRequest = answer.getArgument(2);
return new LineRequest(lineRequest.offsets(), lineRequest.consumer(), lineRequest.config(), lineRequest.numLines(), lineRequest.eventBufferSize(), 42);
});
for (IoctlTestData testData : data) {
when(mock.call(anyInt(), anyLong(), isA(testData.objClass))).thenAnswer(testData.callback::apply);
}
});
}

Expand Down
113 changes: 113 additions & 0 deletions plugins/pi4j-plugin-ffm/src/test/java/com/pi4j/plugin/ffm/unit/GPIOTest.java
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Expand Up @@ -13,9 +13,11 @@
import com.pi4j.plugin.ffm.common.FFMPermissionHelper;
import com.pi4j.plugin.ffm.common.gpio.PinEvent;
import com.pi4j.plugin.ffm.common.gpio.PinFlag;
import com.pi4j.plugin.ffm.common.gpio.enums.LineAttributeId;
import com.pi4j.plugin.ffm.common.gpio.structs.LineAttribute;
import com.pi4j.plugin.ffm.common.gpio.structs.LineEvent;
import com.pi4j.plugin.ffm.common.gpio.structs.LineInfo;
import com.pi4j.plugin.ffm.common.gpio.structs.LineRequest;
import com.pi4j.plugin.ffm.common.poll.PollFlag;
import com.pi4j.plugin.ffm.common.poll.structs.PollingData;
import com.pi4j.plugin.ffm.mocks.*;
Expand Down Expand Up @@ -393,6 +395,117 @@ public void testOutputChangeState() {
}
}

@Test
public void testOutputInitialStateHigh() {
var capturedRequest = new java.util.concurrent.atomic.AtomicReference<LineRequest>();
var lineInfoTestData = new IoctlNativeMock.IoctlTestData(LineInfo.class, (answer) -> {
LineInfo lineInfo = answer.getArgument(2);
return new LineInfo(("Test").getBytes(), ("FFM-Test").getBytes(),
lineInfo.offset(), 0,
PinFlag.OUTPUT.getValue(),
new LineAttribute[0]);
});
var lineRequestTestData = new IoctlNativeMock.IoctlTestData(LineRequest.class, (answer) -> {
LineRequest lineRequest = answer.getArgument(2);
capturedRequest.set(lineRequest);
return new LineRequest(lineRequest.offsets(), lineRequest.consumer(), lineRequest.config(),
lineRequest.numLines(), lineRequest.eventBufferSize(), 42);
});
try (var _ = FileDescriptorNativeMock.setup(GPIOCHIP_FILE);
var _ = IoctlNativeMock.setup(lineInfoTestData, lineRequestTestData)) {

var builder = DigitalOutputConfigBuilder.newInstance()
.bus(-1)
.bcm(9)
.initial(DigitalState.HIGH)
.build();
var pin = pi4j0.digitalOutput().create(builder);

assertEquals(DigitalState.HIGH, pin.state());

var request = capturedRequest.get();
assertNotNull(request, "LineRequest was not sent to the kernel");
var config = request.config();
assertEquals(1, config.numAttrs(), "Initial state should add a single output-values attribute");
var attribute = config.attrs()[0];
assertEquals(LineAttributeId.GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES.getValue(), attribute.attr().id());
// bit 0 corresponds to the single requested line at index 0 in the offsets array
assertEquals(1L, attribute.mask());
assertEquals(1L, attribute.attr().values(), "HIGH initial state should set the line's value bit");
}
}

@Test
public void testOutputInitialStateLowPassedToKernel() {
var capturedRequest = new java.util.concurrent.atomic.AtomicReference<LineRequest>();
var lineInfoTestData = new IoctlNativeMock.IoctlTestData(LineInfo.class, (answer) -> {
LineInfo lineInfo = answer.getArgument(2);
return new LineInfo(("Test").getBytes(), ("FFM-Test").getBytes(),
lineInfo.offset(), 0,
PinFlag.OUTPUT.getValue(),
new LineAttribute[0]);
});
var lineRequestTestData = new IoctlNativeMock.IoctlTestData(LineRequest.class, (answer) -> {
LineRequest lineRequest = answer.getArgument(2);
capturedRequest.set(lineRequest);
return new LineRequest(lineRequest.offsets(), lineRequest.consumer(), lineRequest.config(),
lineRequest.numLines(), lineRequest.eventBufferSize(), 42);
});
try (var _ = FileDescriptorNativeMock.setup(GPIOCHIP_FILE);
var _ = IoctlNativeMock.setup(lineInfoTestData, lineRequestTestData)) {

var builder = DigitalOutputConfigBuilder.newInstance()
.bus(-1)
.bcm(10)
.initial(DigitalState.LOW)
.build();
var pin = pi4j0.digitalOutput().create(builder);

assertEquals(DigitalState.LOW, pin.state());

var request = capturedRequest.get();
assertNotNull(request, "LineRequest was not sent to the kernel");
var config = request.config();
assertEquals(1, config.numAttrs(), "Initial state should add a single output-values attribute");
var attribute = config.attrs()[0];
assertEquals(LineAttributeId.GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES.getValue(), attribute.attr().id());
assertEquals(1L, attribute.mask());
assertEquals(0L, attribute.attr().values(), "LOW initial state should clear the line's value bit");
}
}

@Test
public void testOutputWithoutInitialStateHasNoAttributes() {
var capturedRequest = new java.util.concurrent.atomic.AtomicReference<LineRequest>();
var lineInfoTestData = new IoctlNativeMock.IoctlTestData(LineInfo.class, (answer) -> {
LineInfo lineInfo = answer.getArgument(2);
return new LineInfo(("Test").getBytes(), ("FFM-Test").getBytes(),
lineInfo.offset(), 0,
PinFlag.OUTPUT.getValue(),
new LineAttribute[0]);
});
var lineRequestTestData = new IoctlNativeMock.IoctlTestData(LineRequest.class, (answer) -> {
LineRequest lineRequest = answer.getArgument(2);
capturedRequest.set(lineRequest);
return new LineRequest(lineRequest.offsets(), lineRequest.consumer(), lineRequest.config(),
lineRequest.numLines(), lineRequest.eventBufferSize(), 42);
});
try (var _ = FileDescriptorNativeMock.setup(GPIOCHIP_FILE);
var _ = IoctlNativeMock.setup(lineInfoTestData, lineRequestTestData)) {

var builder = DigitalOutputConfigBuilder.newInstance()
.bus(-1)
.bcm(11)
.build();
pi4j0.digitalOutput().create(builder);

var request = capturedRequest.get();
assertNotNull(request, "LineRequest was not sent to the kernel");
assertEquals(0, request.config().numAttrs(),
"Without an initial state no output-values attribute should be sent");
}
}

@Test
public void testApi() {
var lineInfoTestData = new IoctlNativeMock.IoctlTestData(LineInfo.class, (answer) -> {
Expand Down
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