vdo_validate_header(9)

💅 vdo_validate_header(9) — the kernel API glow-up

Okay so bestie, welcome to vdo_validate_header, a little function from the Kernel API Manual that literally just vibe-checks a header for you. Yes, vdo_validate_header(9) is the whole name, we're not shortening it, it's iconic as-is. 🎀

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✨ NAME ✨

vdo_validate_header — check whether a header matches expectations. That's it, that's the job. A little header bouncer at the club door. 🫶

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🌸 SYNOPSIS 🌸

int vdo_validate_header (const struct header *expected_header , const
       struct header *actual_header , bool exact_size , const char *name );

Look at that signature, she's serving. Four arguments, one int return, no notes. 💅

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🦋 ARGUMENTS 🦋

• expected_header — the expected header. Like, the blueprint, the ideal, the Pinterest board version of what the header should be. 💖
• actual_header — the header being validated. The one that shows up to the group chat and has to prove itself.
• exact_size — if true, the size fields of the two headers must be the same. Otherwise (so if it's false, iykyk) it is required that actual_header.size >= expected_header.size. So no shrinking, only growing. Main character energy only. ⭐
• name — the name of the component or the calling function (for error logging). Basically the @ handle we tag when something goes wrong. 🙈

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💜 DESCRIPTION 💜

It logs an error describing the first mismatch found. Not all of them, bestie — the first one. It finds one problem, gossips about it in the log, and dips. 😭

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🔥 RETURN 🔥

• VDO_SUCCESS — if the header meets expectations. Slay, no notes, she passed the vibe check. ✨
• VDO_INCORRECT_COMPONENT — if the component ids don't match. Not the right component, blocked, report, unfollowed. 💀
• VDO_UNSUPPORTED_VERSION — if the versions or sizes don't match. It's giving "we are not on the same page" and honestly? Relatable. 🙈

Heads up — these three return values are the only ones listed, so don't go inventing extra outcomes. The manpage said what it said. 💅

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👑 SEE ALSO 👑

Kernel file ./drivers/md/dm-vdo/encodings.c and, like, the entire extended universe. The whole friend group, fr fr:

validate_version(9), decode_volume_geometry(9), vdo_encode_volume_geometry(9), vdo_parse_geometry_block(9), vdo_compute_new_forest_pages(9), encode_recovery_journal_state_7_0(9), decode_recovery_journal_state_7_0(9), vdo_get_journal_operation_name(9), encode_slab_depot_state_2_0(9), decode_slab_depot_state_2_0(9), vdo_configure_slab_depot(9), vdo_configure_slab(9), vdo_decode_slab_journal_entry(9), allocate_partition(9), make_partition(9), vdo_initialize_layout(9), vdo_uninitialize_layout(9), vdo_get_partition(9), vdo_get_known_partition(9), pack_vdo_config(9), pack_vdo_component(9), unpack_vdo_config(9), unpack_vdo_component_41_0(9), decode_vdo_component(9), vdo_validate_config(9), vdo_destroy_component_states(9), decode_components(9), vdo_decode_component_states(9), vdo_validate_component_states(9), vdo_encode_component_states(9), vdo_encode_super_block(9), vdo_decode_super_block(9), vdo_initialize_component_states(9), vdo_compute_index_blocks(9), vdo_initialize_volume_geometry(9)

That's 35 entries, and yes I counted because every single one had to be here. Obsessed with the commitment. 🧚

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Okay that's the whole page, bestie — thank you for coming to my TED talk. 💖

This one's brought to you by ./drivers/md/dm-vdo and it's stamped October 2026, filed under vdo_validate_header(9) — mwah, hope this helped, ily, bye! 🎀✨🦋