[PATCH 0/2] platform/x86: dell-laptop: rework kbd_led_level_{get,set}()

[PATCH 0/2] platform/x86: dell-laptop: rework kbd_led_level_{get,set}()

[Yury Norov]

Simplify both functions by replacing open-coded loops and fix
brightness readback for sparse token masks.

Yury Norov (2):
  platform/x86: dell-laptop: Use fns() in kbd_led_level_set()
  platform/x86: dell-laptop: Fix token-based keyboard brightness
    readback

 drivers/platform/x86/dell/dell-laptop.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

-- 
2.53.0

[PATCH 1/2] platform/x86: dell-laptop: Use fns() in kbd_led_level_set()

[Yury Norov]

Replace the loop clearing lower set bits with fns() to select the
supported token corresponding to the requested brightness. Preserve the
zero return when the requested index is out of range.

Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 drivers/platform/x86/dell/dell-laptop.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-laptop.c b/drivers/platform/x86/dell/dell-laptop.c
index 89e85c7f7132..03d3bb70b0d1 100644
--- a/drivers/platform/x86/dell/dell-laptop.c
+++ b/drivers/platform/x86/dell/dell-laptop.c
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/backlight.h>
+#include <linux/bitops.h>
 #include <linux/err.h>
 #include <linux/dmi.h>
 #include <linux/io.h>
@@ -2036,7 +2037,7 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
 	enum led_brightness new_value = value;
 	struct kbd_state state;
 	struct kbd_state new_state;
-	u16 num;
+	unsigned int bit;
 	int ret;
 
 	mutex_lock(&kbd_led_mutex);
@@ -2051,12 +2052,8 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
 			goto out;
 		ret = kbd_set_state_safe(&new_state, &state);
 	} else if (kbd_get_valid_token_counts()) {
-		for (num = kbd_token_bits; num != 0 && value > 0; --value)
-			num &= num - 1; /* clear the first bit set */
-		if (num == 0)
-			ret = 0;
-		else
-			ret = kbd_set_token_bit(ffs(num) - 1);
+		bit = fns(kbd_token_bits, value);
+		ret = bit == BITS_PER_LONG ? 0 : kbd_set_token_bit(bit);
 	} else {
 		pr_warn("Keyboard brightness level control not supported\n");
 		ret = -ENXIO;
-- 
2.53.0

[PATCH 2/2] platform/x86: dell-laptop: Fix token-based keyboard brightness readback

[Yury Norov]

kbd_get_first_active_token_bit() returns an index into kbd_tokens, while
LED brightness is an ordinal among the supported tokens. These differ
when supported token bits are not consecutive starting at bit 0.

Count the supported token bits below the active token with hweight16()
to recover its zero-based brightness ordinal.

Return zero directly when ret == 0: token bit 0 has no supported tokens
below it, so its brightness ordinal is zero.

Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 drivers/platform/x86/dell/dell-laptop.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-laptop.c b/drivers/platform/x86/dell/dell-laptop.c
index 03d3bb70b0d1..55fd48222e5e 100644
--- a/drivers/platform/x86/dell/dell-laptop.c
+++ b/drivers/platform/x86/dell/dell-laptop.c
@@ -2003,7 +2003,6 @@ static const struct attribute_group *kbd_led_groups[] = {
 static enum led_brightness kbd_led_level_get(struct led_classdev *led_cdev)
 {
 	int ret;
-	u16 num;
 	struct kbd_state state;
 
 	if (kbd_get_max_level()) {
@@ -2018,13 +2017,10 @@ static enum led_brightness kbd_led_level_get(struct led_classdev *led_cdev)
 
 	if (kbd_get_valid_token_counts()) {
 		ret = kbd_get_first_active_token_bit();
-		if (ret < 0)
-			return 0;
-		for (num = kbd_token_bits; num != 0 && ret > 0; --ret)
-			num &= num - 1; /* clear the first bit set */
-		if (num == 0)
+		if (ret <= 0)
 			return 0;
-		return ffs(num) - 1;
+		/* Brightness is the active token's rank among supported tokens. */
+		return hweight16(kbd_token_bits & GENMASK(ret - 1, 0));
 	}
 
 	pr_warn("Keyboard brightness level control not supported\n");
-- 
2.53.0