IOSYS_MAP_INIT_OFFSET(9)

💖 IOSYS_MAP_INIT_OFFSET 💖

bestie this one's straight out of the Kernel API Manual and it is so useful — it's the macro that gives your iosys_map a whole new vibe without losing its roots ✨

🎀 NAME 🎀

IOSYS_MAP_INIT_OFFSET — Initializes struct iosys_map from another iosys_map. that's it, that's the tweet 💅

🦋 SYNOPSIS 🦋

IOSYS_MAP_INIT_OFFSET (map_ , offset_ );

🌸 ARGUMENTS 🌸

• map_ — The dma-buf mapping structure to copy from. this is the source map, the one you're building off of, the blueprint 💖
• offset_ — Offset to add to the other mapping. the little nudge forward, yk? the "scoot over" of it all 🫶

🌈 DESCRIPTION 🌈

okay so here's the tea: this macro initializes a new iosys_map struct based on another passed as argument. it does a shallow copy of the struct, which is iconic because it means it's possible to update the back storage without changing where the original map points to. periodt 💅

it's literally the equivalent of doing:

iosys_map map = other_map;
iosys_map_incr(map, offset);

Example usage, bestie:

void foo(struct device *dev, struct iosys_map *base_map)
{
        ...
        struct iosys_map map = IOSYS_MAP_INIT_OFFSET(base_map, FIELD_OFFSET);
        ...
}

The advantage of using the initializer over just increasing the offset with iosys_map_incr like above is that the new map will always point to the right place of the buffer during its scope. it's giving safety, it's giving main character energy 🫶 It reduces the risk of updating the wrong part of the buffer and having no compiler warning about that. and like, if the assignment to IOSYS_MAP_INIT_OFFSET is forgotten, the compiler can warn about the use of uninitialized variable. chefs kiss 👑

💜 SEE ALSO 💜

• Kernel file ./include/linux/iosys-map.h overview(9)
• struct iosys_map(9)
• IOSYS_MAP_INIT_VADDR(9)
• IOSYS_MAP_INIT_VADDR_IOMEM(9)
• iosys_map_set_vaddr(9)
• iosys_map_set_vaddr_iomem(9)
• iosys_map_is_equal(9)
• iosys_map_is_null(9)
• iosys_map_is_set(9)
• iosys_map_clear(9)
• iosys_map_memcpy_to(9)
• iosys_map_memcpy_from(9)
• iosys_map_incr(9)
• iosys_map_memset(9)
• iosys_map_rd(9)
• iosys_map_wr(9)
• iosys_map_rd_field(9)
• iosys_map_wr_field(9)

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and that's the whole page, bestie! brought to you by ./include/linux, dated October 2026, IOSYS_MAP_INIT_OFFSET(9) in the Kernel API Manual 💖✨ now go slay those buffer offsets 🎀👑