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Subject[PATCH v8] iio: Handle enumerated properties with gaps
Date
From: Lars-Peter Clausen <lars@metafoo.de>

Some enums might have gaps or reserved values in the middle of their value
range. E.g. consider a 2-bit enum where the values 0, 1 and 3 have a
meaning, but 2 is a reserved value and can not be used.

Add support for such enums to the IIO enum helper functions. A reserved
values is marked by setting its entry in the items array to NULL rather
than the normal descriptive string value.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---

Changelog v7 -> v8:
* https://lore.kernel.org/linux-iio/20210107084434.35283-1-alexandru.ardelean@analog.com/
* dropped patch 'lib/string.c: add __sysfs_match_string_with_gaps() helper'
* merged __sysfs_match_string_with_gaps into drivers/iio/industrial-core.c
as iio_sysfs_match_string_with_gaps()

drivers/iio/industrialio-core.c | 39 ++++++++++++++++++++++++++++++---
1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index e9ee9363fed0..db20e2ab437d 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -169,6 +169,36 @@ static const char * const iio_chan_info_postfix[] = {
[IIO_CHAN_INFO_CALIBAMBIENT] = "calibambient",
};

+/**
+ * iio_sysfs_match_string_with_gaps - matches given string in an array with gaps
+ * @array: array of strings
+ * @n: number of strings in the array
+ * @str: string to match with
+ *
+ * Returns index of @str in the @array or -EINVAL, similar to match_string().
+ * Uses sysfs_streq instead of strcmp for matching.
+ *
+ * This routine will look for a string in an array of strings.
+ * The search will continue until the element is found or the n-th element
+ * is reached, regardless of any NULL elements in the array.
+ */
+static int iio_sysfs_match_string_with_gaps(const char * const *array, size_t n,
+ const char *str)
+{
+ const char *item;
+ int index;
+
+ for (index = 0; index < n; index++) {
+ item = array[index];
+ if (!item)
+ continue;
+ if (sysfs_streq(item, str))
+ return index;
+ }
+
+ return -EINVAL;
+}
+
#if defined(CONFIG_DEBUG_FS)
/*
* There's also a CONFIG_DEBUG_FS guard in include/linux/iio/iio.h for
@@ -470,8 +500,11 @@ ssize_t iio_enum_available_read(struct iio_dev *indio_dev,
if (!e->num_items)
return 0;

- for (i = 0; i < e->num_items; ++i)
+ for (i = 0; i < e->num_items; ++i) {
+ if (!e->items[i])
+ continue;
len += scnprintf(buf + len, PAGE_SIZE - len, "%s ", e->items[i]);
+ }

/* replace last space with a newline */
buf[len - 1] = '\n';
@@ -492,7 +525,7 @@ ssize_t iio_enum_read(struct iio_dev *indio_dev,
i = e->get(indio_dev, chan);
if (i < 0)
return i;
- else if (i >= e->num_items)
+ else if (i >= e->num_items || !e->items[i])
return -EINVAL;

return snprintf(buf, PAGE_SIZE, "%s\n", e->items[i]);
@@ -509,7 +542,7 @@ ssize_t iio_enum_write(struct iio_dev *indio_dev,
if (!e->set)
return -EINVAL;

- ret = __sysfs_match_string(e->items, e->num_items, buf);
+ ret = iio_sysfs_match_string_with_gaps(e->items, e->num_items, buf);
if (ret < 0)
return ret;

--
2.17.1
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