backlight: aw99706: Validate all DT property values consistently

The lookup helpers for dim-mode and ramp-ctl take a shortcut when
lookup_tbl is NULL: they accept any u32 value without range-checking
and return success unconditionally. Out-of-range values get silently
truncated by regmap_update_bits instead of triggering the dev_warn +
default-fallback path that the other properties use.

Add a field-width check for the NULL-table case so that values
exceeding the register field maximum are rejected the same way a
table-lookup miss is.

The switching frequency table has a second hole: reserved slots use 0
as their marker, so "awinic,sw-freq-hz = <0>" matches slot 0 and
programs a reserved encoding. Make the reserved marker U32_MAX and
skip such slots during lookup.

While here, also switch the error returns to -EINVAL for consistency.

Fixes: 147b38a5ad06 ("backlight: aw99706: Add support for Awinic AW99706 backlight")
Signed-off-by: Junjie Cao <junjie.cao@linux.dev>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Link: https://patch.msgid.link/20260804030255.1934470-3-junjie.cao@intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

0 files changed, 0 insertions, 0 deletions