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Chunfeng Song
6fb0a9d907
The hand-written bitfield offsets in is_link_up(), is_autoneg_enabled() and is_autoneg_completed() were correct when the abstraction was merged: at that time autoneg, link, and autoneg_complete were at bits 13, 14, and 15 of struct phy_device's first bitfield unit. Commit2796ff1e3d("net: phy: add flag is_genphy_driven to struct phy_device") later inserted is_genphy_driven just before autoneg, shifting the three fields up by one, so the accessors now read: is_link_up() reads bit 14 = autoneg is_autoneg_enabled() reads bit 13 = is_genphy_driven is_autoneg_completed() reads bit 15 = link The official ax88796b Rust driver uses all three accessors in its read_status() implementation, so it inherits the bug. phy_attach_direct() sets is_genphy_driven only when it falls back to the generic driver, and ax88796b has a real driver, so is_genphy_driven stays 0. The broken is_autoneg_enabled() therefore reads bit 13 as 0, compares it against AUTONEG_ENABLE (1), and always returns false, so read_status() never reaches the resolve_aneg_linkmode() call. The ordinary bindgen accessors take &self. Calling them through (*phydev).link() would create a shared reference to the complete bindings::phy_device, which is not appropriate for an object wrapped in Opaque. Use the bindgen-generated raw accessors (link_raw(), autoneg_raw(), and autoneg_complete_raw()) instead. They retain the bit positions and endianness handling generated from the C layout without creating a Rust reference to the complete phy_device. Drop the hand-written numbers together with the TODO comment that marked them as a stopgap. The raw accessors are only emitted by bindgen 0.71 and later, and were added at the Rust-for-Linux project's request, so this fix can only be backported to stable branches whose minimum bindgen version is at least that, hence the scope on the Cc: stable line below. Found by a static equivalence audit (C2RustDrv, a C-to-Rust driver migration tool) that compares hand-written bitfield offsets against the bindgen layout of struct phy_device. Verified by building the bindings and checking the generated accessors; no runtime testing was possible without PHY hardware. Fixes:2796ff1e3d("net: phy: add flag is_genphy_driven to struct phy_device") Cc: [email protected] # Only 7.1.y and later (requires bindgen's raw pointer accessors). Link: https://github.com/rust-lang/rust-bindgen/issues/2674 Signed-off-by: Chunfeng Song <[email protected]> Reviewed-by: FUJITA Tomonori <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Jakub Kicinski <[email protected]>