Added more capabilities checks for I2C

Signed-off-by: Erik Agsjö <erik.agsjo@gmail.com>

drivers/i2c/i2c_test.go

@@ -5,15 +5,31 @@ import (
 
 	"gobot.io/x/gobot/gobottest"
 	"gobot.io/x/gobot/sysfs"
+	"syscall"
+	"unsafe"
 )
 
+func syscallImpl(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err syscall.Errno) {
+	if (trap == syscall.SYS_IOCTL) && (a2 == sysfs.I2C_FUNCS) {
+		var funcPtr *uint64 = (*uint64)(unsafe.Pointer(a3))
+		*funcPtr = sysfs.I2C_FUNC_SMBUS_READ_BYTE | sysfs.I2C_FUNC_SMBUS_READ_BYTE_DATA |
+			sysfs.I2C_FUNC_SMBUS_READ_WORD_DATA |
+			sysfs.I2C_FUNC_SMBUS_WRITE_BYTE | sysfs.I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
+			sysfs.I2C_FUNC_SMBUS_WRITE_WORD_DATA
+	}
+	// Let all operations succeed
+	return 0, 0, 0
+}
+
 func initI2CDevice() sysfs.I2cDevice {
 	fs := sysfs.NewMockFilesystem([]string{
 		"/dev/i2c-1",
 	})
 	sysfs.SetFilesystem(fs)
 
-	sysfs.SetSyscall(&sysfs.MockSyscall{})
+	sysfs.SetSyscall(&sysfs.MockSyscall{
+		Impl: syscallImpl,
+	})
 	i, _ := sysfs.NewI2cDevice("/dev/i2c-1")
 	return i
 }

sysfs/i2c_device.go

@@ -9,6 +9,7 @@ import (
 )
 
 const (
+	// From  /usr/include/linux/i2c-dev.h:
 	// ioctl signals
 	I2C_SLAVE = 0x0703
 	I2C_FUNCS = 0x0705
@@ -16,7 +17,15 @@ const (
 	// Read/write markers
 	I2C_SMBUS_READ  = 1
 	I2C_SMBUS_WRITE = 0
+
+	// From  /usr/include/linux/i2c.h:
 	// Adapter functionality
+	I2C_FUNC_SMBUS_READ_BYTE        = 0x00020000
+	I2C_FUNC_SMBUS_WRITE_BYTE       = 0x00040000
+	I2C_FUNC_SMBUS_READ_BYTE_DATA   = 0x00080000
+	I2C_FUNC_SMBUS_WRITE_BYTE_DATA  = 0x00100000
+	I2C_FUNC_SMBUS_READ_WORD_DATA   = 0x00200000
+	I2C_FUNC_SMBUS_WRITE_WORD_DATA  = 0x00400000
 	I2C_FUNC_SMBUS_READ_BLOCK_DATA  = 0x01000000
 	I2C_FUNC_SMBUS_WRITE_BLOCK_DATA = 0x02000000
 	// Transaction types
@@ -108,35 +117,59 @@ func (d *i2cDevice) Close() (err error) {
 }
 
 func (d *i2cDevice) ReadByte() (val uint8, err error) {
+	if d.funcs&I2C_FUNC_SMBUS_READ_BYTE == 0 {
+		return 0, fmt.Errorf("SMBus read byte not supported")
+	}
+
 	var data uint8
 	err = d.smbusAccess(I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, uintptr(unsafe.Pointer(&data)))
 	return data, err
 }
 
 func (d *i2cDevice) ReadByteData(reg uint8) (val uint8, err error) {
+	if d.funcs&I2C_FUNC_SMBUS_READ_BYTE_DATA == 0 {
+		return 0, fmt.Errorf("SMBus read byte data not supported")
+	}
+
 	var data uint8
 	err = d.smbusAccess(I2C_SMBUS_READ, reg, I2C_SMBUS_BYTE_DATA, uintptr(unsafe.Pointer(&data)))
 	return data, err
 }
 
 func (d *i2cDevice) ReadWordData(reg uint8) (val uint16, err error) {
+	if d.funcs&I2C_FUNC_SMBUS_READ_WORD_DATA == 0 {
+		return 0, fmt.Errorf("SMBus read word data not supported")
+	}
+
 	var data uint16
 	err = d.smbusAccess(I2C_SMBUS_READ, reg, I2C_SMBUS_WORD_DATA, uintptr(unsafe.Pointer(&data)))
 	return data, err
 }
 
 func (d *i2cDevice) WriteByte(val uint8) (err error) {
+	if d.funcs&I2C_FUNC_SMBUS_WRITE_BYTE == 0 {
+		return fmt.Errorf("SMBus write byte not supported")
+	}
+
 	err = d.smbusAccess(I2C_SMBUS_WRITE, val, I2C_SMBUS_BYTE, uintptr(0))
 	return err
 }
 
 func (d *i2cDevice) WriteByteData(reg uint8, val uint8) (err error) {
+	if d.funcs&I2C_FUNC_SMBUS_WRITE_BYTE_DATA == 0 {
+		return fmt.Errorf("SMBus write byte data not supported")
+	}
+
 	var data = val
 	err = d.smbusAccess(I2C_SMBUS_WRITE, reg, I2C_SMBUS_BYTE_DATA, uintptr(unsafe.Pointer(&data)))
 	return err
 }
 
 func (d *i2cDevice) WriteWordData(reg uint8, val uint16) (err error) {
+	if d.funcs&I2C_FUNC_SMBUS_WRITE_WORD_DATA == 0 {
+		return fmt.Errorf("SMBus write word data not supported")
+	}
+
 	var data = val
 	err = d.smbusAccess(I2C_SMBUS_WRITE, reg, I2C_SMBUS_WORD_DATA, uintptr(unsafe.Pointer(&data)))
 	return err

sysfs/syscall.go

@@ -13,7 +13,9 @@ type SystemCaller interface {
 type NativeSyscall struct{}
 
 // MockSyscall represents the mock Syscall
-type MockSyscall struct{}
+type MockSyscall struct {
+	Impl func(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err syscall.Errno)
+}
 
 var sys SystemCaller = &NativeSyscall{}
 
@@ -34,5 +36,9 @@ func (sys *NativeSyscall) Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err
 
 // Syscall implements the SystemCaller interface
 func (sys *MockSyscall) Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err syscall.Errno) {
-	return 0, 0, 0
+	if sys.Impl != nil {
+		return sys.Impl(trap, a1, a2, a3)
+	} else {
+		return 0, 0, 0
+	}
 }