[libgpiod][PATCH v4 03/20] bindings: cxx: add support for bias flags

[Kent Gibson <warthog618@gmail.com>]

Add support for bias flags in line requests and returning the line bias
setting via a bias accessor.

Based on initial work by Drew Fustini <drew@pdp7.com>.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 bindings/cxx/gpiod.hpp     | 26 ++++++++++++++++++++++++++
 bindings/cxx/line.cpp      | 19 +++++++++++++++++++
 bindings/cxx/line_bulk.cpp |  6 ++++++
 3 files changed, 51 insertions(+)

diff --git a/bindings/cxx/gpiod.hpp b/bindings/cxx/gpiod.hpp
index b5a9401..2b1a6ab 100644
--- a/bindings/cxx/gpiod.hpp
+++ b/bindings/cxx/gpiod.hpp
@@ -233,6 +233,12 @@ struct line_request
 	/**< The line is an open-source port. */
 	GPIOD_API static const ::std::bitset<32> FLAG_OPEN_DRAIN;
 	/**< The line is an open-drain port. */
+	GPIOD_API static const ::std::bitset<32> FLAG_BIAS_DISABLE;
+	/**< The line has neither pull-up nor pull-down resistor enabled */
+	GPIOD_API static const ::std::bitset<32> FLAG_BIAS_PULL_DOWN;
+	/**< The line has a configurable pull-down resistor enabled */
+	GPIOD_API static const ::std::bitset<32> FLAG_BIAS_PULL_UP;
+	/**< The line has a configurable pull-up resistor enabled */
 
 	::std::string consumer;
 	/**< Consumer name to pass to the request. */
@@ -320,6 +326,12 @@ public:
 	 */
 	GPIOD_API int active_state(void) const;
 
+	/**
+	 * @brief Get current bias of this line.
+	 * @return Current bias setting.
+	 */
+	GPIOD_API int bias(void) const;
+
 	/**
 	 * @brief Check if this line is used by the kernel or other user space
 	 *        process.
@@ -456,6 +468,20 @@ public:
 		/**< Line's active state is high. */
 	};
 
+	/**
+	 * @brief Possible bias settings.
+	 */
+	enum : int {
+		BIAS_AS_IS = 1,
+		/**< Line's bias state is unknown. */
+		BIAS_DISABLE,
+		/**< Line's internal bias is disabled. */
+		BIAS_PULL_UP,
+		/**< Line's internal pull-up bias is enabled. */
+		BIAS_PULL_DOWN,
+		/**< Line's internal pull-down bias is enabled. */
+	};
+
 private:
 
 	line(::gpiod_line* line, const chip& owner);
diff --git a/bindings/cxx/line.cpp b/bindings/cxx/line.cpp
index df6eada..29ea5b2 100644
--- a/bindings/cxx/line.cpp
+++ b/bindings/cxx/line.cpp
@@ -6,10 +6,22 @@
  */
 
 #include <gpiod.hpp>
+#include <map>
 #include <system_error>
 
 namespace gpiod {
 
+namespace {
+
+const ::std::map<int, int> bias_mapping = {
+	{ GPIOD_LINE_BIAS_PULL_UP,	line::BIAS_PULL_UP, },
+	{ GPIOD_LINE_BIAS_PULL_DOWN,	line::BIAS_PULL_DOWN, },
+	{ GPIOD_LINE_BIAS_DISABLE,	line::BIAS_DISABLE, },
+	{ GPIOD_LINE_BIAS_AS_IS,	line::BIAS_AS_IS, },
+};
+
+} /* namespace */
+
 line::line(void)
 	: _m_line(nullptr),
 	  _m_chip()
@@ -67,6 +79,13 @@ int line::active_state(void) const
 	return active == GPIOD_LINE_ACTIVE_STATE_HIGH ? ACTIVE_HIGH : ACTIVE_LOW;
 }
 
+int line::bias(void) const
+{
+	this->throw_if_null();
+
+	return bias_mapping.at(::gpiod_line_bias(this->_m_line));
+}
+
 bool line::is_used(void) const
 {
 	this->throw_if_null();
diff --git a/bindings/cxx/line_bulk.cpp b/bindings/cxx/line_bulk.cpp
index c708c8b..5f1cac4 100644
--- a/bindings/cxx/line_bulk.cpp
+++ b/bindings/cxx/line_bulk.cpp
@@ -14,6 +14,9 @@ namespace gpiod {
 const ::std::bitset<32> line_request::FLAG_ACTIVE_LOW(GPIOD_BIT(0));
 const ::std::bitset<32> line_request::FLAG_OPEN_SOURCE(GPIOD_BIT(1));
 const ::std::bitset<32> line_request::FLAG_OPEN_DRAIN(GPIOD_BIT(2));
+const ::std::bitset<32> line_request::FLAG_BIAS_DISABLE(GPIOD_BIT(3));
+const ::std::bitset<32> line_request::FLAG_BIAS_PULL_DOWN(GPIOD_BIT(4));
+const ::std::bitset<32> line_request::FLAG_BIAS_PULL_UP(GPIOD_BIT(5));
 
 namespace {
 
@@ -38,6 +41,9 @@ const ::std::map<::std::bitset<32>, int, bitset_cmp> reqflag_mapping = {
 	{ line_request::FLAG_ACTIVE_LOW,	GPIOD_LINE_REQUEST_FLAG_ACTIVE_LOW, },
 	{ line_request::FLAG_OPEN_DRAIN,	GPIOD_LINE_REQUEST_FLAG_OPEN_DRAIN, },
 	{ line_request::FLAG_OPEN_SOURCE,	GPIOD_LINE_REQUEST_FLAG_OPEN_SOURCE, },
+	{ line_request::FLAG_BIAS_DISABLE,	GPIOD_LINE_REQUEST_FLAG_BIAS_DISABLE, },
+	{ line_request::FLAG_BIAS_PULL_DOWN,	GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_DOWN, },
+	{ line_request::FLAG_BIAS_PULL_UP,	GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_UP, },
 };
 
 } /* namespace */
-- 
2.24.0