Patch "pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pinctrl-single-fix-pcs_parse_bits_in_pinctrl_entry-to-use-__ffs-than-ffs.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Keerthy <[email protected]>
Date: Thu, 14 Apr 2016 10:29:16 +0530
Subject: pinctrl: single: Fix pcs_parse_bits_in_pinctrl_entry to use __ffs than ffs

From: Keerthy <[email protected]>

commit 56b367c0cd67d4c3006738e7dc9dda9273fd2bfe upstream.

pcs_parse_bits_in_pinctrl_entry uses ffs which gives bit indices ranging from 1 to MAX. This leads to a corner case where we try to request the pin number = MAX and fails.

bit_pos value is being calculted using ffs. pin_num_from_lsb uses bit_pos value. pins array is populated with:

pin + pin_num_from_lsb.

The above is 1 more than usual bit indices as bit_pos uses ffs to compute first set bit. Hence the last of the pins array is populated with the MAX value and not MAX - 1 which causes error when we call pin_request.

mask_pos is rightly calculated as ((pcs->fmask) << (bit_pos - 1)) Consequently val_pos and submask are correct.

Hence use __ffs which gives (ffs(x) - 1) as the first bit set.

---
 drivers/pinctrl/pinctrl-single.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -1273,9 +1273,9 @@ static int pcs_parse_bits_in_pinctrl_ent
 
 		/* Parse pins in each row from LSB */
 		while (mask) {
-			bit_pos = ffs(mask);
+			bit_pos = __ffs(mask);
 			pin_num_from_lsb = bit_pos / pcs->bits_per_pin;
-			mask_pos = ((pcs->fmask) << (bit_pos - 1));
+			mask_pos = ((pcs->fmask) << bit_pos);
 			val_pos = val & mask_pos;
 			submask = mask & mask_pos;
 

@@ -1844,7 +1844,7 @@ static int pcs_probe(struct platform_dev
 	ret = of_property_read_u32(np, "pinctrl-single,function-mask",
 				   &pcs->fmask);
 	if (!ret) {
-		pcs->fshift = ffs(pcs->fmask) - 1;
+		pcs->fshift = __ffs(pcs->fmask);
 		pcs->fmax = pcs->fmask >> pcs->fshift;
 	} else {
 		/* If mask property doesn't exist, function mux is invalid. */

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/pinctrl-single-fix-pcs_parse_bits_in_pinctrl_entry-to-use-__ffs-than-ffs.patch