[libgpiod][PATCH v2 6/8] bindings: python: add the output_values argument to Chip.request_lines()

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Add a new optional argument to Chip.request_lines() called output_values.
It accepts a dictionary of mappings between line names or offsets to the
output values the requested lines should be set to at request-time.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 bindings/python/gpiod/chip.py               | 30 ++++++++++
 bindings/python/gpiod/ext/line-config.c     | 64 +++++++++++++++++++++
 bindings/python/tests/tests_line_request.py | 55 ++++++++++++++++++
 3 files changed, 149 insertions(+)

diff --git a/bindings/python/gpiod/chip.py b/bindings/python/gpiod/chip.py
index ad2eddd..97ff340 100644
--- a/bindings/python/gpiod/chip.py
+++ b/bindings/python/gpiod/chip.py
@@ -6,10 +6,12 @@ from .chip_info import ChipInfo
 from .exception import ChipClosedError
 from .info_event import InfoEvent
 from .internal import poll_fd
+from .line import Value
 from .line_info import LineInfo
 from .line_settings import LineSettings, _line_settings_to_ext
 from .line_request import LineRequest
 from collections import Counter
+from collections.abc import Iterable
 from datetime import timedelta
 from errno import ENOENT
 from select import select
@@ -221,6 +223,7 @@ class Chip:
         config: dict[tuple[Union[int, str]], Optional[LineSettings]],
         consumer: Optional[str] = None,
         event_buffer_size: Optional[int] = None,
+        output_values: Optional[dict[tuple[Union[int, str]], Value]] = None,
     ) -> LineRequest:
         """
         Request a set of lines for exclusive usage.
@@ -234,6 +237,10 @@ class Chip:
             Consumer string to use for this request.
           event_buffer_size:
             Size of the kernel edge event buffer to configure for this request.
+          output_values:
+            Dictionary mapping offsets or names to line.Value. This can be used
+            to set the desired output values globally while reusing LineSettings
+            for more lines.
 
         Returns:
           New LineRequest object.
@@ -260,10 +267,20 @@ class Chip:
                     )
                 )
 
+        # If we have global output values - map line names to offsets
+        if output_values:
+            mapped_output_values = {
+                self.line_offset_from_id(line): value
+                for line, value in output_values.items()
+            }
+        else:
+            mapped_output_values = None
+
         for lines, settings in config.items():
             offsets = list()
             name_map = dict()
             offset_map = dict()
+            global_output_values = list()
 
             if isinstance(lines, int) or isinstance(lines, str):
                 lines = (lines,)
@@ -271,6 +288,16 @@ class Chip:
             for line in lines:
                 offset = self.line_offset_from_id(line)
                 offsets.append(offset)
+
+                # If there's a global output value for this offset, store it in the
+                # list for later.
+                if mapped_output_values:
+                    global_output_values.append(
+                        mapped_output_values[offset]
+                        if offset in mapped_output_values
+                        else Value.INACTIVE
+                    )
+
                 if isinstance(line, str):
                     name_map[line] = offset
                     offset_map[offset] = line
@@ -279,6 +306,9 @@ class Chip:
                 offsets, _line_settings_to_ext(settings or LineSettings())
             )
 
+        if len(global_output_values):
+            line_cfg.set_output_values(global_output_values)
+
         req_internal = self._chip.request_lines(line_cfg, consumer, event_buffer_size)
         request = LineRequest(req_internal)
 
diff --git a/bindings/python/gpiod/ext/line-config.c b/bindings/python/gpiod/ext/line-config.c
index 173ca6b..0bba112 100644
--- a/bindings/python/gpiod/ext/line-config.c
+++ b/bindings/python/gpiod/ext/line-config.c
@@ -89,12 +89,76 @@ line_config_add_line_settings(line_config_object *self, PyObject *args)
 	Py_RETURN_NONE;
 }
 
+static PyObject *
+line_config_set_output_values(line_config_object *self, PyObject *args)
+{
+	PyObject *values, *iter, *next, *val_stripped;
+	enum gpiod_line_value *valbuf;
+	Py_ssize_t num_values, pos;
+	int ret;
+
+	values = PyTuple_GetItem(args, 0);
+	if (!values)
+		return NULL;
+
+	num_values = PyObject_Size(values);
+	if (num_values < 0)
+		return NULL;
+
+	valbuf = PyMem_Calloc(num_values, sizeof(*valbuf));
+	if (!valbuf)
+		return PyErr_NoMemory();
+
+	iter = PyObject_GetIter(values);
+	if (!iter) {
+		PyMem_Free(valbuf);
+		return NULL;
+	}
+
+	for (pos = 0;; pos++) {
+		next = PyIter_Next(iter);
+		if (!next) {
+			Py_DECREF(iter);
+			break;
+		}
+
+		val_stripped = PyObject_GetAttrString(next, "value");
+		Py_DECREF(next);
+		if (!val_stripped) {
+			PyMem_Free(valbuf);
+			Py_DECREF(iter);
+			return NULL;
+		}
+
+		valbuf[pos] = PyLong_AsLong(val_stripped);
+		Py_DECREF(val_stripped);
+		if (PyErr_Occurred()) {
+			PyMem_Free(valbuf);
+			Py_DECREF(iter);
+			return NULL;
+		}
+	}
+
+	ret = gpiod_line_config_set_output_values(self->cfg,
+						  valbuf, num_values);
+	PyMem_Free(valbuf);
+	if (ret)
+		return Py_gpiod_SetErrFromErrno();	
+
+	Py_RETURN_NONE;
+}
+
 static PyMethodDef line_config_methods[] = {
 	{
 		.ml_name = "add_line_settings",
 		.ml_meth = (PyCFunction)line_config_add_line_settings,
 		.ml_flags = METH_VARARGS,
 	},
+	{
+		.ml_name = "set_output_values",
+		.ml_meth = (PyCFunction)line_config_set_output_values,
+		.ml_flags = METH_VARARGS,
+	},
 	{ }
 };
 
diff --git a/bindings/python/tests/tests_line_request.py b/bindings/python/tests/tests_line_request.py
index c0ac768..096ec7c 100644
--- a/bindings/python/tests/tests_line_request.py
+++ b/bindings/python/tests/tests_line_request.py
@@ -402,6 +402,61 @@ class LineRequestConsumerString(TestCase):
             self.assertEqual(info.consumer, "?")
 
 
+class LineRequestSetOutputValues(TestCase):
+    def setUp(self):
+        self.sim = gpiosim.Chip(
+            num_lines=4, line_names={0: "foo", 1: "bar", 2: "baz", 3: "xyz"}
+        )
+
+    def tearDown(self):
+        del self.sim
+
+    def test_request_with_globally_set_output_values(self):
+        with gpiod.request_lines(
+            self.sim.dev_path,
+            config={(0, 1, 2, 3): gpiod.LineSettings(direction=Direction.OUTPUT)},
+            output_values={
+                0: Value.ACTIVE,
+                1: Value.INACTIVE,
+                2: Value.ACTIVE,
+                3: Value.INACTIVE,
+            },
+        ) as request:
+            self.assertEqual(self.sim.get_value(0), SimVal.ACTIVE)
+            self.assertEqual(self.sim.get_value(1), SimVal.INACTIVE)
+            self.assertEqual(self.sim.get_value(2), SimVal.ACTIVE)
+            self.assertEqual(self.sim.get_value(3), SimVal.INACTIVE)
+
+    def test_request_with_globally_set_output_values_with_mapping(self):
+        with gpiod.request_lines(
+            self.sim.dev_path,
+            config={(0, 1, 2, 3): gpiod.LineSettings(direction=Direction.OUTPUT)},
+            output_values={"baz": Value.ACTIVE, "foo": Value.ACTIVE},
+        ) as request:
+            self.assertEqual(self.sim.get_value(0), SimVal.ACTIVE)
+            self.assertEqual(self.sim.get_value(1), SimVal.INACTIVE)
+            self.assertEqual(self.sim.get_value(2), SimVal.ACTIVE)
+            self.assertEqual(self.sim.get_value(3), SimVal.INACTIVE)
+
+    def test_request_with_globally_set_output_values_bad_mapping(self):
+        with self.assertRaises(FileNotFoundError):
+            with gpiod.request_lines(
+                self.sim.dev_path,
+                config={(0, 1, 2, 3): gpiod.LineSettings(direction=Direction.OUTPUT)},
+                output_values={"foobar": Value.ACTIVE},
+            ) as request:
+                pass
+
+    def test_request_with_globally_set_output_values_bad_offset(self):
+        with self.assertRaises(ValueError):
+            with gpiod.request_lines(
+                self.sim.dev_path,
+                config={(0, 1, 2, 3): gpiod.LineSettings(direction=Direction.OUTPUT)},
+                output_values={5: Value.ACTIVE},
+            ) as request:
+                pass
+
+
 class ReconfigureRequestedLines(TestCase):
     def setUp(self):
         self.sim = gpiosim.Chip(num_lines=8, line_names={3: "foo", 4: "bar", 6: "baz"})
-- 
2.37.2