# DF-2095 — intel_dp_aux_set_pwm_freq u8 loop underflow infinite loop

## Verdict
REPRODUCED (source-only confirmation). Bug confirmed by source tracing.

## Mechanism
intel_dp_aux_backlight.c: pn is u8 (line 114). Loop for(pn=pn_max;pn>=pn_min;pn--) at line 156: when pn_min=0, pn decrements 0->255 (u8 wrap), 255>=0 true -> infinite loop. 1<<pn with pn>31 is UB.

## Fix
Change loop variable pn from u8 to int; keep pn_min/pn_max as u8 for dpcd_readb.

## Batch-build status
Applied with all 24 other fixes; kernel + modules compiled **rc=0, 0 errors, -Werror**.