Commit 6543f376 authored by Matti Vaittinen's avatar Matti Vaittinen Committed by Jonathan Cameron
Browse files

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: default avatarMatti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/ef61c2c1e9a1c5e9f713f656871fdcb1652afdc2.1697452986.git.mazziesaccount@gmail.com


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent 2718f154

drivers/iio/industrialio-buffer.c

+16 −0
Original line number Diff line number Diff line
@@ -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))