adc: 64bit gain inversion function

Add a variant of `adc_gain_invert` that operates on an `int64_t` instead
of `int32_t`.

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

drivers/adc/adc_common.c

@@ -6,36 +6,52 @@
 
 #include <zephyr/drivers/adc.h>
 
-int adc_gain_invert(enum adc_gain gain,
-		    int32_t *value)
+struct gain_desc {
+	uint8_t mul;
+	uint8_t div;
+};
+static const struct gain_desc gains[] = {
+	[ADC_GAIN_1_6] = {.mul = 6, .div = 1},
+	[ADC_GAIN_1_5] = {.mul = 5, .div = 1},
+	[ADC_GAIN_1_4] = {.mul = 4, .div = 1},
+	[ADC_GAIN_2_7] = {.mul = 7, .div = 2},
+	[ADC_GAIN_1_3] = {.mul = 3, .div = 1},
+	[ADC_GAIN_2_5] = {.mul = 5, .div = 2},
+	[ADC_GAIN_1_2] = {.mul = 2, .div = 1},
+	[ADC_GAIN_2_3] = {.mul = 3, .div = 2},
+	[ADC_GAIN_4_5] = {.mul = 5, .div = 4},
+	[ADC_GAIN_1] = {.mul = 1, .div = 1},
+	[ADC_GAIN_2] = {.mul = 1, .div = 2},
+	[ADC_GAIN_3] = {.mul = 1, .div = 3},
+	[ADC_GAIN_4] = {.mul = 1, .div = 4},
+	[ADC_GAIN_6] = {.mul = 1, .div = 6},
+	[ADC_GAIN_8] = {.mul = 1, .div = 8},
+	[ADC_GAIN_12] = {.mul = 1, .div = 12},
+	[ADC_GAIN_16] = {.mul = 1, .div = 16},
+	[ADC_GAIN_24] = {.mul = 1, .div = 24},
+	[ADC_GAIN_32] = {.mul = 1, .div = 32},
+	[ADC_GAIN_64] = {.mul = 1, .div = 64},
+	[ADC_GAIN_128] = {.mul = 1, .div = 128},
+};
+
+int adc_gain_invert(enum adc_gain gain, int32_t *value)
+{
+	int rv = -EINVAL;
+
+	if ((uint8_t)gain < ARRAY_SIZE(gains)) {
+		const struct gain_desc *gdp = &gains[gain];
+
+		if ((gdp->mul != 0) && (gdp->div != 0)) {
+			*value = (gdp->mul * *value) / gdp->div;
+			rv = 0;
+		}
+	}
+
+	return rv;
+}
+
+int adc_gain_invert_64(enum adc_gain gain, int64_t *value)
 {
-	struct gain_desc {
-		uint8_t mul;
-		uint8_t div;
-	};
-	static const struct gain_desc gains[] = {
-		[ADC_GAIN_1_6] = {.mul = 6, .div = 1},
-		[ADC_GAIN_1_5] = {.mul = 5, .div = 1},
-		[ADC_GAIN_1_4] = {.mul = 4, .div = 1},
-		[ADC_GAIN_2_7] = {.mul = 7, .div = 2},
-		[ADC_GAIN_1_3] = {.mul = 3, .div = 1},
-		[ADC_GAIN_2_5] = {.mul = 5, .div = 2},
-		[ADC_GAIN_1_2] = {.mul = 2, .div = 1},
-		[ADC_GAIN_2_3] = {.mul = 3, .div = 2},
-		[ADC_GAIN_4_5] = {.mul = 5, .div = 4},
-		[ADC_GAIN_1] = {.mul = 1, .div = 1},
-		[ADC_GAIN_2] = {.mul = 1, .div = 2},
-		[ADC_GAIN_3] = {.mul = 1, .div = 3},
-		[ADC_GAIN_4] = {.mul = 1, .div = 4},
-		[ADC_GAIN_6] = {.mul = 1, .div = 6},
-		[ADC_GAIN_8] = {.mul = 1, .div = 8},
-		[ADC_GAIN_12] = {.mul = 1, .div = 12},
-		[ADC_GAIN_16] = {.mul = 1, .div = 16},
-		[ADC_GAIN_24] = {.mul = 1, .div = 24},
-		[ADC_GAIN_32] = {.mul = 1, .div = 32},
-		[ADC_GAIN_64] = {.mul = 1, .div = 64},
-		[ADC_GAIN_128] = {.mul = 1, .div = 128},
-	};
 	int rv = -EINVAL;
 
 	if ((uint8_t)gain < ARRAY_SIZE(gains)) {

include/zephyr/drivers/adc.h

@@ -71,8 +71,25 @@ enum adc_gain {
  * @retval 0 if the gain was successfully reversed
  * @retval -EINVAL if the gain could not be interpreted
  */
-int adc_gain_invert(enum adc_gain gain,
-		    int32_t *value);
+int adc_gain_invert(enum adc_gain gain, int32_t *value);
+
+/**
+ * @brief Invert the application of gain to a measurement value.
+ *
+ * For example, if the gain passed in is ADC_GAIN_1_6 and the
+ * referenced value is 10, the value after the function returns is 60.
+ *
+ * @param gain the gain used to amplify the input signal.
+ *
+ * @param value a pointer to a value that initially has the effect of
+ * the applied gain but has that effect removed when this function
+ * successfully returns.  If the gain cannot be reversed the value
+ * remains unchanged.
+ *
+ * @retval 0 if the gain was successfully reversed
+ * @retval -EINVAL if the gain could not be interpreted
+ */
+int adc_gain_invert_64(enum adc_gain gain, int64_t *value);
 
 /** @brief ADC references. */
 enum adc_reference {