pvr_ioctl_u...adding_check(9)

💖 NAME 💖

okay so welcome to the pvr_ioctl_u...adding_check(9) page in the Kernel API Manual — the main character is pvr_ioctl_union_padding_check(9), and her whole job is to validate that the implicit padding between the end of a union member and the end of the union itself is zeroed. no cap. 💅

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✨ SYNOPSIS ✨

bool pvr_ioctl_union_padding_check (void *instance , size_t union_offset
       , size_t union_size , size_t member_size );

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🧚 ARGUMENTS 🧚

the whole cast, in order, bestie:

• instance — Pointer to the instance of the struct to validate.
• union_offset — Offset into the type of instance of the target union. Must be 64-bit aligned.
• union_size — Size of the target union in the type of instance. Must be 64-bit aligned.
• member_size — Size of the target member in the target union specified by union_offset and union_size. It is assumed that the offset of the target member is zero relative to union_offset. Must be 64-bit aligned.

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🦋 DESCRIPTION 🦋

okay so lowkey you probably want to use PVR_IOCTL_UNION_PADDING_CHECK instead of calling this function directly, since that macro abstracts away much of the setup, and also provides some static validation. See its docs for details. it’s giving “let the macro handle the annoying bits” energy ✨

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🎀 RETURN 🎀

the vibe check comes back as:

• true if every byte between the end of the used member of the union and the end of that union is zeroed, or
• false otherwise.

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🌈 SEE ALSO 🌈

Kernel file ./drivers/gpu/drm/imagination/pvr_device.h, plus the whole squad:

• struct pvr_gpu_id(9)
• struct pvr_fw_version(9)
• struct pvr_device_data(9)
• struct pvr_device(9)
• struct pvr_file(9)
• PVR_HAS_FEATURE(9)
• PVR_FEATURE_VALUE(9)
• PVR_HAS_QUIRK(9)
• PVR_HAS_ENHANCEMENT(9)
• PVR_PACKED_BVNC(9)
• pvr_gpu_id_to_packed_bvnc(9)
• PVR_CR_FIELD_GET(9)
• pvr_cr_read32(9)
• pvr_cr_read64(9)
• pvr_cr_write32(9)
• pvr_cr_write64(9)
• pvr_cr_poll_reg32(9)
• pvr_cr_poll_reg64(9)
• pvr_round_up_to_cacheline_size(9)
• IOCTL validation helpers(9)
• PVR_STATIC_ASSERT_64BIT_ALIGNED(9)
• PVR_IOCTL_UNION_PADDING_CHECK(9)

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mwah 💋 — source/version: ./drivers/gpu/drm/imagination; date: October 2026; page title: pvr_ioctl_u...adding_check(9). bye bestie, go zero that padding 🫶