backlight: qcom-wled: Override default length with qcom,enabled-strings

[ 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@somainline.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211115203459.1634079-6-marijn.suijten@somainline.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index dbcbeda..c057368 100644 (file)
--- 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;