DMA-coherent allocations (CoherentAllocation/Coherent/dma::Pool) bound
their element type on kernel::transmute::{AsBytes, FromBytes}. This RFC
lets a type satisfy that bound by deriving zerocopy's byte-safety traits
instead of a hand-written unsafe impl.
The bound cannot be switched to zerocopy wholesale (some DMA structs are
unions that IntoBytes cannot derive), and a blanket bridge impl is
rejected by coherence. So the series bridges the two per type:
1. add the bridge macro impl_transmute_via_zerocopy!, which emits the
transmute impls only for a zerocopy-derived type.
2. re-export zerocopy::Immutable from the prelude.
3-4. worked example: convert nova-core's GspMem and msgq POD types.
This series was prepared with the Claude Code AI assistant (model
claude-opus-4-8): it drafted the macro, the nova-core conversion and the
changelogs, which the submitter reviewed and takes responsibility for. It
was verified by building nova-core on rust-next and a negative test
confirming IntoBytes rejects mis-sized padding. See
Documentation/process/coding-assistants.rst.
Assisted-by: Claude-Code:claude-opus-4-8
Signed-off-by: SeungJong Ha <[email protected]>
---
SeungJong Ha (4):
rust: transmute: add `impl_transmute_via_zerocopy!` macro
rust: prelude: re-export `zerocopy::Immutable`
gpu: nova-core: gsp: derive zerocopy traits for the msgq POD types
gpu: nova-core: gsp: convert GspMem to zerocopy via the transmute bridge
drivers/gpu/nova-core/gsp.rs | 13 ++-------
drivers/gpu/nova-core/gsp/cmdq.rs | 15 +++++-----
drivers/gpu/nova-core/gsp/fw.rs | 8 +++---
drivers/gpu/nova-core/gsp/fw/r570_144.rs | 2 ++
drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs | 4 +--
rust/kernel/prelude.rs | 2 ++
rust/kernel/transmute.rs | 35 +++++++++++++++++++++++
7 files changed, 54 insertions(+), 25 deletions(-)
---
base-commit: 780d569e6c4b422290f5cba319eb904b355d64be
change-id: 20260628-dma-zerocopy-bridge-dc1c96b610cf
Best regards,
--
SeungJong Ha <[email protected]>
