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panic_qr: use new #[export] macro

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This validates at compile time that the signatures match what is in the
header file. It highlights one annoyance with the compile-time check,
which is that it can only be used with functions marked unsafe.

If the function is not unsafe, then this error is emitted:

error[E0308]: `if` and `else` have incompatible types
   --> <linux>/drivers/gpu/drm/drm_panic_qr.rs:987:19
    |
986 | #[export]
    | --------- expected because of this
987 | pub extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected unsafe fn, found safe fn
    |
    = note: expected fn item `unsafe extern "C" fn(_, _) -> _ {kernel::bindings::drm_panic_qr_max_data_size}`
               found fn item `extern "C" fn(_, _) -> _ {drm_panic_qr_max_data_size}`

The signature declarations are moved to a header file so it can be
included in the Rust bindings helper, and the extern keyword is removed
as it is unnecessary.

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Simona Vetter <simona.vetter@ffwll.ch>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250303-export-macro-v3-5-41fbad85a27f@google.com
[ Fixed `rustfmt`. Moved on top the unsafe requirement comment to follow
  the usual style, and slightly reworded it for clarity. Formatted
  bindings helper comment. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Alice Ryhl 2025-03-03 08:45:16 +00:00 committed by Miguel Ojeda
parent 92d2873bed
commit fc2f191f85
4 changed files with 21 additions and 9 deletions
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5
drivers/gpu/drm/drm_panic.c
View File

@ -486,11 +486,6 @@ static void drm_panic_qr_exit(void)
stream.workspace = NULL;
}
extern size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);
extern u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,
u8 *tmp, size_t tmp_size);
static int drm_panic_get_qr_code_url(u8 **qr_image)
{
struct kmsg_dump_iter iter;

13
drivers/gpu/drm/drm_panic_qr.rs
View File

@ -27,7 +27,7 @@
//! * <https://github.com/bjguillot/qr>
use core::cmp;
use kernel::str::CStr;
use kernel::{prelude::*, str::CStr};
#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd)]
struct Version(usize);
@ -929,7 +929,7 @@ impl QrImage<'_> {
/// * `tmp` must be valid for reading and writing for `tmp_size` bytes.
///
/// They must remain valid for the duration of the function call.
#[no_mangle]
#[export]
pub unsafe extern "C" fn drm_panic_qr_generate(
url: *const kernel::ffi::c_char,
data: *mut u8,
@ -980,8 +980,13 @@ pub unsafe extern "C" fn drm_panic_qr_generate(
/// * If `url_len` > 0, remove the 2 segments header/length and also count the
/// conversion to numeric segments.
/// * If `url_len` = 0, only removes 3 bytes for 1 binary segment.
#[no_mangle]
pub extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {
///
/// # Safety
///
/// Always safe to call.
// Required to be unsafe due to the `#[export]` annotation.
#[export]
pub unsafe extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {
#[expect(clippy::manual_range_contains)]
if version < 1 || version > 40 {
return 0;

7
include/drm/drm_panic.h
View File

@ -163,4 +163,11 @@ static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags)
#endif
#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);
u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,
u8 *tmp, size_t tmp_size);
#endif
#endif /* __DRM_PANIC_H__ */

5
rust/bindings/bindings_helper.h
View File

@ -37,6 +37,11 @@
#include <linux/workqueue.h>
#include <trace/events/rust_sample.h>
#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
// Used by `#[export]` in `drivers/gpu/drm/drm_panic_qr.rs`.
#include <drm/drm_panic.h>
#endif
/* `bindgen` gets confused at certain things. */
const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN;
const size_t RUST_CONST_HELPER_PAGE_SIZE = PAGE_SIZE;