Wrote MatrixConfig type

src/lib.rs

@@ -8,3 +8,46 @@ pub struct TCA8418<I2C> {
     i2c: I2C,
 }
 
+#[derive(Clone, Copy)]
+pub struct MatrixConfig {
+    rows: u8,
+    columns: u16,
+}
+
+impl MatrixConfig {
+    /// A new config where the matrix has no rows or columns and all of the pins are
+    /// allocated for GPIO.
+    pub const fn new_empty() -> Self {
+        MatrixConfig {
+            rows: 0,
+            columns: 0,
+        }
+    }
+
+    /// Add a row to the keyboard matrix, meaning its pin will not be available for GPIO.
+    ///
+    /// `row_number` must be in the range `0..=7`
+    pub const fn with_row(self, row_number: u8) -> Self {
+        if row_number >= 8 {
+            panic!("row_number out of bounds");
+        }
+        MatrixConfig {
+            rows: self.rows | (1 << row_number),
+            columns: self.columns,
+        }
+    }
+
+    /// Add a column to the keyboard matrix, meaning its pin will not be available for GPIO.
+    ///
+    /// `column_number` must be in the range `0..=9`
+    pub const fn with_column(self, column_number: u8) -> Self {
+        if column_number >= 10 {
+            panic!("column_number out of bounds");
+        }
+        MatrixConfig {
+            rows: self.rows,
+            columns: self.columns | (1 << column_number),
+        }
+    }
+}
+