Claude review: misc: fastrpc: Add missing bug fixes

[Claude Code Review Bot <claude-review@example.com>]

Overall Series Review

Subject: misc: fastrpc: Add missing bug fixes
Author: Jianping Li <jianping.li@oss.qualcomm.com>
Patches: 1
Reviewed: 2026-05-16T09:15:13.576580

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This is a 5-patch series fixing memory management issues in the FastRPC driver, focused on the Audio PD remote heap. The core problem is well-motivated: userspace-controlled alloc/free of the reserved memory region shared with the DSP is unsafe because the kernel cannot know when the DSP is done with the buffers. The solution moves the reserved memory lifecycle to be tied to the rpmsg channel (probe/remove).

The series has some real fixes (patches 1, 2) and a significant architectural change (patch 4) that restructures how Audio PD memory is handled. However, **patch 4 has several concerning issues** including a memory leak on error, incomplete initialization of the `remote_heap` struct, and questionable use of a spinlock around non-atomic operations. Patch 3 is effectively superseded by patch 4 — it adds validation that patch 4 then restructures, making the Fixes/stable tags on patch 3 questionable.

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