py-smbus: Fix i2c_smbus_* error propagation

The Python bindings haven't been updated after commit
330bba29f3 ("libi2c: Properly
propagate real error codes on read errors"). This led to erronenous
behavior every time an error other than -1 is returned by i2c_smbus_*
functions.

[JD: Edited description.]

Signed-off-by: Georgii Staroselskii <georgii.staroselskii@emlid.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>

CHANGES

@@ -11,6 +11,7 @@ master
                 Documentation update for DDR4
                 Verify the CRC of DDR4 data block 1
   eeprog: Fix ambiguous parentheses
+  py-smbus: Fix i2c_smbus_* error propagation
 
 4.0 (2017-10-30)
   tools: Fix build with recent compilers (gcc 4.6+)

py-smbus/smbusmodule.c

@@ -216,7 +216,7 @@ SMBus_read_byte(SMBus *self, PyObject *args)
 
 	SMBus_SET_ADDR(self, addr);
 
-	if ((result = i2c_smbus_read_byte(self->fd)) == -1) {
+	if ((result = i2c_smbus_read_byte(self->fd)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -239,7 +239,7 @@ SMBus_write_byte(SMBus *self, PyObject *args)
 
 	SMBus_SET_ADDR(self, addr);
 
-	if ((result = i2c_smbus_write_byte(self->fd, (__u8)val)) == -1) {
+	if ((result = i2c_smbus_write_byte(self->fd, (__u8)val)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -263,7 +263,7 @@ SMBus_read_byte_data(SMBus *self, PyObject *args)
 
 	SMBus_SET_ADDR(self, addr);
 
-	if ((result = i2c_smbus_read_byte_data(self->fd, (__u8)cmd)) == -1) {
+	if ((result = i2c_smbus_read_byte_data(self->fd, (__u8)cmd)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -287,7 +287,7 @@ SMBus_write_byte_data(SMBus *self, PyObject *args)
 	SMBus_SET_ADDR(self, addr);
 
 	if ((result = i2c_smbus_write_byte_data(self->fd,
-				(__u8)cmd, (__u8)val)) == -1) {
+				(__u8)cmd, (__u8)val)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -311,7 +311,7 @@ SMBus_read_word_data(SMBus *self, PyObject *args)
 
 	SMBus_SET_ADDR(self, addr);
 
-	if ((result = i2c_smbus_read_word_data(self->fd, (__u8)cmd)) == -1) {
+	if ((result = i2c_smbus_read_word_data(self->fd, (__u8)cmd)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -335,7 +335,7 @@ SMBus_write_word_data(SMBus *self, PyObject *args)
 	SMBus_SET_ADDR(self, addr);
 
 	if ((result = i2c_smbus_write_word_data(self->fd,
-				(__u8)cmd, (__u16)val)) == -1) {
+				(__u8)cmd, (__u16)val)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}
@@ -360,7 +360,7 @@ SMBus_process_call(SMBus *self, PyObject *args)
 	SMBus_SET_ADDR(self, addr);
 
 	if ((result = i2c_smbus_process_call(self->fd,
-				(__u8)cmd, (__u16)val)) == -1) {
+				(__u8)cmd, (__u16)val)) < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		return NULL;
 	}