Claude review: drm/i915/dp: Add member to intel_dp to store AS SDP v2 support

Claude Code Review Bot
2026-03-31T07:39:47Z

Patch Review

**Bug:** `drm_dp_dpcd_read_byte()` returns **0 on success**, not 1:
```c
+ if (drm_dp_dpcd_read_byte(&intel_dp->aux,
+ DP_DPRX_FEATURE_ENUMERATION_LIST_CONT_1,
+ &rx_features) == 1) {
```
This check will always be false (the function returns 0 on success, negative on error). The same issue applies to the second `drm_dp_dpcd_read_byte` call for `pr_caps`. This means `as_sdp_v2_supported` will never be set to true.

Should be:
```c
if (drm_dp_dpcd_read_byte(..., &rx_features) == 0) {
```

Note: the older `drm_dp_dpcd_readb()` API returned number of bytes read (1 on success), but `drm_dp_dpcd_read_byte()` returns 0 on success. The author likely confused the two APIs. No R-b tag.

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