Claude review: gpu: host1x: Fix passing zero to ERR_PTR in host1x_iommu_attach()

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Overall Series Review

Subject: gpu: host1x: Fix passing zero to ERR_PTR in
 host1x_iommu_attach()
Author: Alper Ak <alperyasinak1@gmail.com>
Patches: 1
Reviewed: 2026-02-11T17:05:33.927031

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This is a single patch submission that addresses an error handling bug in the host1x IOMMU attachment code. The patch fixes a violation of the ERR_PTR/IS_ERR contract where ERR_PTR(0) could be returned, which evaluates to NULL and breaks the error handling convention in kernel code.

**Series Assessment:**
- **Scope**: Appropriately focused on a single bug fix
- **Target**: Correctly marked for stable backport (Cc: stable@vger.kernel.org)
- **Static Analysis Finding**: Identified by Smatch, which is a legitimate source for such bugs
- **Fix Quality**: The fix needs careful examination of the broader error handling semantics

**Key Concerns:**
1. The fix changes error handling semantics in a subtle way that requires validation
2. Need to verify all callers handle both NULL and ERR_PTR return values correctly
3. The original code path's intention when setting err=0 needs clarification

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