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Message-Id: <20260123-adf41513-iio-driver-v5-2-2dce812a2dda@analog.com>
Date: Fri, 23 Jan 2026 15:53:07 +0000
From: Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@...nel.org>
To: linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-doc@...r.kernel.org
Cc: Jonathan Cameron <jic23@...nel.org>,
David Lechner <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Michael Hennerich <Michael.Hennerich@...log.com>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Jonathan Corbet <corbet@....net>,
Rodrigo Alencar <rodrigo.alencar@...log.com>
Subject: [PATCH v5 2/8] iio: core: add fixed point parsing with 64-bit
parts
From: Rodrigo Alencar <rodrigo.alencar@...log.com>
Add iio_str_to_fixpoint64() function that leverages simple_strtoull()
to parse numbers from a string.
A helper function __iio_str_to_fixpoint64() replaces
__iio_str_to_fixpoint() implementation, extending its usage for
64-bit fixed-point parsing.
Signed-off-by: Rodrigo Alencar <rodrigo.alencar@...log.com>
---
drivers/iio/industrialio-core.c | 151 +++++++++++++++++++++++++++-------------
include/linux/iio/iio.h | 2 +
2 files changed, 103 insertions(+), 50 deletions(-)
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index f69deefcfb6f..4ad4f1b29421 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -881,6 +881,77 @@ static ssize_t iio_read_channel_info_avail(struct device *dev,
}
}
+/**
+ * __iio_str_to_fixpoint64() - Parse a fixed-point number from a string
+ * @str: The string to parse
+ * @fract_mult: Multiplier for the first decimal place, should be a power of 10
+ * @integer: The integer part of the number
+ * @fract: The fractional part of the number
+ * @scale_db: True if this should parse as dB
+ *
+ * This variant uses 64-bit integers for both integer and fractional parts.
+ *
+ * Returns:
+ * 0 on success, or a negative error code if the string could not be parsed.
+ */
+static int __iio_str_to_fixpoint64(const char *str, u64 fract_mult,
+ s64 *integer, s64 *fract, bool scale_db)
+{
+ u64 i = 0, f = 0;
+ char *end;
+ int digit_count, precision = ffs(fract_mult);
+ bool negative = false;
+
+ if (str[0] == '-') {
+ negative = true;
+ str++;
+ } else if (str[0] == '+') {
+ str++;
+ }
+
+ i = simple_strtoull(str, &end, 10);
+ digit_count = end - str;
+ if (digit_count > 20)
+ return -EINVAL;
+
+ if (precision && *end == '.') {
+ str = end + 1;
+ f = simple_strtoull(str, &end, 10);
+ digit_count = end - str;
+ if (!digit_count || digit_count > 20)
+ return -EINVAL;
+
+ if (digit_count > precision) {
+ digit_count -= precision;
+ f = div64_u64(f, int_pow(10, digit_count));
+ } else {
+ digit_count = precision - digit_count;
+ f *= int_pow(10, digit_count);
+ }
+ } else if (!digit_count) {
+ return -EINVAL;
+ }
+
+ if (scale_db) {
+ /* Ignore the dB suffix */
+ if (!strncmp(end, " dB", sizeof(" dB") - 1))
+ end += sizeof(" dB") - 1;
+ else if (!strncmp(end, "dB", sizeof("dB") - 1))
+ end += sizeof("dB") - 1;
+ }
+
+ if (*end == '\n')
+ end++;
+
+ if (*end != '\0')
+ return -EINVAL;
+
+ *integer = (negative && i) ? -i : i;
+ *fract = (negative && !i) ? -f : f;
+
+ return 0;
+}
+
/**
* __iio_str_to_fixpoint() - Parse a fixed-point number from a string
* @str: The string to parse
@@ -895,63 +966,43 @@ static ssize_t iio_read_channel_info_avail(struct device *dev,
static int __iio_str_to_fixpoint(const char *str, int fract_mult,
int *integer, int *fract, bool scale_db)
{
- int i = 0, f = 0;
- bool integer_part = true, negative = false;
+ s64 integer64, fract64;
+ int ret;
- if (fract_mult == 0) {
- *fract = 0;
+ ret = __iio_str_to_fixpoint64(str, fract_mult, &integer64, &fract64,
+ scale_db);
+ if (ret)
+ return ret;
- return kstrtoint(str, 0, integer);
- }
+ if (integer64 < INT_MIN || integer64 > INT_MAX ||
+ fract64 < INT_MIN || fract64 > INT_MAX)
+ return -ERANGE;
- if (str[0] == '-') {
- negative = true;
- str++;
- } else if (str[0] == '+') {
- str++;
- }
-
- while (*str) {
- if ('0' <= *str && *str <= '9') {
- if (integer_part) {
- i = i * 10 + *str - '0';
- } else {
- f += fract_mult * (*str - '0');
- fract_mult /= 10;
- }
- } else if (*str == '\n') {
- if (*(str + 1) == '\0')
- break;
- return -EINVAL;
- } else if (!strncmp(str, " dB", sizeof(" dB") - 1) && scale_db) {
- /* Ignore the dB suffix */
- str += sizeof(" dB") - 1;
- continue;
- } else if (!strncmp(str, "dB", sizeof("dB") - 1) && scale_db) {
- /* Ignore the dB suffix */
- str += sizeof("dB") - 1;
- continue;
- } else if (*str == '.' && integer_part) {
- integer_part = false;
- } else {
- return -EINVAL;
- }
- str++;
- }
-
- if (negative) {
- if (i)
- i = -i;
- else
- f = -f;
- }
-
- *integer = i;
- *fract = f;
+ *integer = integer64;
+ *fract = fract64;
return 0;
}
+/**
+ * iio_str_to_fixpoint64() - Parse a fixed-point number from a string
+ * @str: The string to parse
+ * @fract_mult: Multiplier for the first decimal place, should be a power of 10
+ * @integer: The integer part of the number
+ * @fract: The fractional part of the number
+ *
+ * This variant uses 64-bit integers for both integer and fractional parts.
+ *
+ * Returns:
+ * 0 on success, or a negative error code if the string could not be parsed.
+ */
+int iio_str_to_fixpoint64(const char *str, u64 fract_mult, s64 *integer,
+ s64 *fract)
+{
+ return __iio_str_to_fixpoint64(str, fract_mult, integer, fract, false);
+}
+EXPORT_SYMBOL_GPL(iio_str_to_fixpoint64);
+
/**
* iio_str_to_fixpoint() - Parse a fixed-point number from a string
* @str: The string to parse
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 872ebdf0dd77..432cd26fc9d0 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -940,6 +940,8 @@ int iio_active_scan_mask_index(struct iio_dev *indio_dev);
ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals);
+int iio_str_to_fixpoint64(const char *str, u64 fract_mult, s64 *integer,
+ s64 *fract);
int iio_str_to_fixpoint(const char *str, int fract_mult, int *integer,
int *fract);
--
2.43.0
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