Re: [PATCH v3 1/2] rust: uapi: add zerocopy/zerocopy_derive

["Gary Guo" <gary@garyguo.net>]

On Sat Sep 26, 2026 at 1:26 AM BST, Deborah Brouwer wrote:
> Make the zerocopy and zerocopy_derive crates available for use when
> building the UAPI crate and its tests. Then attempt to derive most of
> the zerocopy traits for struct drm_panthor_gpu_info when generating its
> binding. This will be used by the Tyr driver that needs the traits
> IntoBytes and Immutable to safely copy the struct byte-for-byte to
> userspace.
>
> Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
> ---
>  rust/Makefile           | 12 +++++++++---
>  rust/bindgen_parameters |  3 +++
>  2 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/rust/Makefile b/rust/Makefile
> index da1a7409d984..bf02a1efd6f3 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -365,8 +365,11 @@ rusttestlib-bindings: private rustc_target_flags = --extern ffi --extern pin_ini
>  rusttestlib-bindings: $(src)/bindings/lib.rs rusttestlib-ffi rusttestlib-pin_init FORCE
>  	+$(call if_changed,rustc_test_library)
>  
> -rusttestlib-uapi: private rustc_target_flags = --extern ffi --extern pin_init
> -rusttestlib-uapi: $(src)/uapi/lib.rs rusttestlib-ffi rusttestlib-pin_init FORCE
> +rusttestlib-uapi: private rustc_target_flags = --extern ffi --extern pin_init \
> +	--extern zerocopy=$(objtree)/$(obj)/test/libzerocopy.rlib \
> +	--extern zerocopy_derive=$(objtree)/$(obj)/test/$(libzerocopy_derive_name)
> +rusttestlib-uapi: $(src)/uapi/lib.rs rusttestlib-ffi rusttestlib-pin_init \
> +	rusttestlib-zerocopy rusttestlib-zerocopy_derive FORCE
>  	+$(call if_changed,rustc_test_library)
>  
>  quiet_cmd_rustdoc_test = RUSTDOC T $<
> @@ -782,11 +785,14 @@ $(obj)/bindings.o: $(src)/bindings/lib.rs \
>      $(obj)/bindings/bindings_helpers_generated.rs FORCE
>  	+$(call if_changed_rule,rustc_library)
>  
> -$(obj)/uapi.o: private rustc_target_flags = --extern ffi --extern pin_init
> +$(obj)/uapi.o: private rustc_target_flags = --extern ffi --extern pin_init \
> +	--extern zerocopy --extern zerocopy_derive
>  $(obj)/uapi.o: private skip_gendwarfksyms = 1
>  $(obj)/uapi.o: $(src)/uapi/lib.rs \
>      $(obj)/ffi.o \
>      $(obj)/pin_init.o \
> +    $(obj)/zerocopy.o \
> +    $(obj)/$(libzerocopy_derive_name) \

Please add these to `bindings` crate as well to avoid have it diverging with
`uapi`.

>      $(obj)/uapi/uapi_generated.rs FORCE
>  	+$(call if_changed_rule,rustc_library)
>  
> diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
> index 8402b0c93545..332bc8d6a9f7 100644
> --- a/rust/bindgen_parameters
> +++ b/rust/bindgen_parameters
> @@ -71,3 +71,6 @@
>  # Structs should implement `Zeroable` when all of their fields do.
>  --with-derive-custom-struct .*=MaybeZeroable
>  --with-derive-custom-union .*=MaybeZeroable
> +
> +# `drm_panthor_gpu_info` is copied byte-for-byte to userspace.
> +--with-derive-custom-struct '^drm_panthor_gpu_info$'=zerocopy_derive::most_traits

This is Tyr specific change and should be in patch 2.

Best,
Gary