Re: [PATCH v4 2/4] backlight: qcom-wled: Fix WLED3 brightness register stride
From: David Heidelberg
Date: Mon Sep 21 2026 - 07:18:34 EST
On 21/09/2026 13:08, Konrad Dybcio wrote:
On 9/21/26 12:46 PM, David Heidelberg via B4 Relay wrote:
From: David Heidelberg <david@xxxxxxx>
WLED3 has a 16-bit brightness register pair per string, at 0x40 + 2*n,
which is what the pm8941-wled driver wrote to:
rc = regmap_bulk_write(wled->regmap,
wled->addr + WLED3_CTRL_REG_VAL_BASE + 2 * i,
v, 2);
The restructuring for WLED3 turned that into WLED3_SINK_REG_BRIGHT(n),
defined as 0x40 + n, so the two byte writes for consecutive strings
overlap: string 1 overwrites the MSB of string 0 with its own LSB, and
with the default three strings only string 1 ends up with the requested
value.
Use the 2 byte stride.
Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: David Heidelberg <david@xxxxxxx>
---
drivers/video/backlight/qcom-wled.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index 2281007bdd459..f452d328997ad 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -54,17 +54,17 @@
#define WLED3_SINK_REG_SYNC 0x47
#define WLED3_SINK_REG_SYNC_CLEAR 0x00
#define WLED3_SINK_REG_CURR_SINK 0x4f
#define WLED3_SINK_REG_CURR_SINK_MASK GENMASK(7, 5)
#define WLED3_SINK_REG_CURR_SINK_SHFT 5
/* WLED3 specific per-'string' registers below */
-#define WLED3_SINK_REG_BRIGHT(n) (0x40 + n)
+#define WLED3_SINK_REG_BRIGHT(n) (0x40 + (n * 0x2))
Ideally n would be wrapped in its own parentheses (doesn't
checkpatch warn against that?)
Yeah it does, thou not sure it make sense here.
If needed, I'll send another version with it... :)
Thanks
David
Reviewed-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
Konrad