Re: [PATCH v5 0/5] nouveau/gsp: Clean up IS_ERR vs IS_ERR_OR_NULL usage

[Hongling Zeng <zhongling0719@126.com>]

  Hi

   Sorry for the noise. The v5 patch fully addresses all documentation 
issues and passes AI testing with no code changes. A similar fix 
"sunrpc: Fix error handling in
   rpc_sysfs_xprt_switch_add_xprt_store()" has already been accepted by 
the community.

   Please review when you have time.

   Thanks!

在 2026年06月22日 16:11, Hongling Zeng 写道:
> This series addresses feedback from Danilo Krummrich and Timur Tabi
> regarding the use of IS_ERR() vs IS_ERR_OR_NULL() in the nouveau
> GSP RPC code.
>
> The key insight is that we should align error checking with the actual
> return value contracts of each function:
> - Functions that never return NULL should use IS_ERR()
> - Functions that can return NULL should use IS_ERR_OR_NULL()
>
> This version adds documentation to clarify the return value contracts,
> making it easier for maintainers to validate future changes.
>
> Return Value Analysis
>
> After thorough code analysis, the RPC functions are categorized as:
>
> Never return NULL (use IS_ERR):**
> - r535_gsp_msgq_peek()
> - r535_gsp_msgq_recv_one_elem()
> - r535_gsp_rpc_get()
>
> CAN return NULL (use IS_ERR_OR_NULL):**
> - r535_gsp_msgq_recv() - returns NULL when RPC length is invalid
> - r535_gsp_msg_recv() - returns NULL when queue drained
> - r535_gsp_rpc_handle_reply() - returns NULL for NOWAIT/NOSEQ policies
> - r535_gsp_rpc_send() - can return NULL via handle_reply
> - r535_gsp_rpc_push() - can return NULL via handle_reply
>
> Changes in v2
>
> - Added kernel-doc comments documenting return value contracts for all
>    RPC functions
> - Cleaned up incorrect IS_ERR_OR_NULL() usage for functions that never
>    return NULL
> - Kept IS_ERR_OR_NULL() in places where NULL is actually possible
> - Added Fixes tags to all patches
>
> Testing
>
> This fixes the NULL pointer dereference oops that occurs during
> nouveau initialization on some systems.
>
> Patches
>
> Hongling Zeng (5):
>    nouveau/gsp/rpc: Document RPC function return value contracts
>    nouveau/gsp/rpc: Cleanup incorrect IS_ERR_OR_NULL in rpc.c
>    nouveau/gsp/rm/alloc: Cleanup IS_ERR_OR_NULL usage
>    nouveau/gsp/rm/bar: Cleanup IS_ERR_OR_NULL usage
>    nouveau/gsp: Cleanup IS_ERR_OR_NULL in nvkm_gsp_rpc_rd()
>
>   drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h   | 2 +-
>   .../gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/alloc.c | 2 +-
>   .../gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/bar.c  | 2 +-
>   .../gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/rpc.c  | 81 ++++++++++++++++++-
>   4 files changed, 81 insertions(+), 6 deletions(-)