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authorMatti Vaittinen <mazziesaccount@gmail.com>2023-10-16 14:04:55 +0300
committerJonathan Cameron <Jonathan.Cameron@huawei.com>2023-11-16 19:10:28 +0000
commit6543f376ec8aa90a6c1ed44b765f4f0d6c3eb1db (patch)
tree275d146cbe4ec19255389bd42ee599ba061af44f /drivers/iio/industrialio-buffer.c
parent2718f15403fbbff4c4116824e02537e39342986a (diff)
iio: buffer: document known issue
Add documentation explaining why the code which scans all available scan masks is checking only a single long worth of bits even though the code was intended to be supporting masks wider than single long. Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> Link: https://lore.kernel.org/r/ef61c2c1e9a1c5e9f713f656871fdcb1652afdc2.1697452986.git.mazziesaccount@gmail.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/iio/industrialio-buffer.c')
-rw-r--r--drivers/iio/industrialio-buffer.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 176d31d9f9d8..09c41e9ccf87 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -413,6 +413,22 @@ static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
{
if (bitmap_empty(mask, masklength))
return NULL;
+ /*
+ * The condition here do not handle multi-long masks correctly.
+ * It only checks the first long to be zero, and will use such mask
+ * as a terminator even if there was bits set after the first long.
+ *
+ * Correct check would require using:
+ * while (!bitmap_empty(av_masks, masklength))
+ * instead. This is potentially hazardous because the
+ * avaliable_scan_masks is a zero terminated array of longs - and
+ * using the proper bitmap_empty() check for multi-long wide masks
+ * would require the array to be terminated with multiple zero longs -
+ * which is not such an usual pattern.
+ *
+ * As writing of this no multi-long wide masks were found in-tree, so
+ * the simple while (*av_masks) check is working.
+ */
while (*av_masks) {
if (strict) {
if (bitmap_equal(mask, av_masks, masklength))