[PATCH 5.15 289/846] backlight: qcom-wled: Override default length with qcom,enabled-strings

[Greg Kroah-Hartman]

From: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>

[ Upstream commit 2b4b49602f9feca7b7a84eaa33ad9e666c8aa695 ]

The length of qcom,enabled-strings as property array is enough to
determine the number of strings to be enabled, without needing to set
qcom,num-strings to override the default number of strings when less
than the default (which is also the maximum) is provided in DT.

This also introduces an extra warning when qcom,num-strings is set,
denoting that it is not necessary to set both anymore.  It is usually
more concise to set just qcom,num-length when a zero-based, contiguous
range of strings is needed (the majority of the cases), or to only set
qcom,enabled-strings when a specific set of indices is desired.

Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3")
Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxxx>
Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211115203459.1634079-6-marijn.suijten@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/video/backlight/qcom-wled.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index dbcbeda655192..c057368e5056e 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -1521,6 +1521,8 @@ static int wled_configure(struct wled *wled)
 				return -EINVAL;
 			}
 		}
+
+		cfg->num_strings = string_len;
 	}
 
 	rc = of_property_read_u32(dev->of_node, "qcom,num-strings", &val);
@@ -1531,9 +1533,13 @@ static int wled_configure(struct wled *wled)
 			return -EINVAL;
 		}
 
-		if (string_len > 0 && val > string_len) {
-			dev_err(dev, "qcom,num-strings exceeds qcom,enabled-strings\n");
-			return -EINVAL;
+		if (string_len > 0) {
+			dev_warn(dev, "Only one of qcom,num-strings or qcom,enabled-strings"
+				      " should be set\n");
+			if (val > string_len) {
+				dev_err(dev, "qcom,num-strings exceeds qcom,enabled-strings\n");
+				return -EINVAL;
+			}
 		}
 
 		cfg->num_strings = val;
-- 
2.34.1