iio: Handle enumerated properties with gaps

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>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210107112049.10815-1-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index e9ee936..7db761a 100644 (file)
--- 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;