iosys_map_rd(9)

💜 iosys_map_rd — the Kernel API Manual bestie 💜

Okay so, hi, welcome to iosys_map_rd(9), a little function from the Kernel API Manual that literally just reads a value out of an iosys_map for you ✨

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🌸 NAME 🌸

iosys_map_rd — read a C-type value from the iosys_map, that's it, that's the whole gig 🫶

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🎀 SYNOPSIS 🎀

iosys_map_rd (map__ , offset__ , type__ );

Three args, no drama, we love a clean signature 💅

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🦋 ARGUMENTS 🦋

• map__ — the iosys_map structure itself. like, the map you're reading from, bestie.
• offset__ — the offset you're reading from. yes, exactly where you think it is 📍
• type__ — the type of the value being read. tell it what you're pulling out 👑

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✨ DESCRIPTION ✨

So what it does is, it reads a C-type value from iosys_map. and when we say C-type value, we mean it: u8, u16, u32 and u64. those four. that's the whole lineup 🎀

🚨 Real talk though: for other types, or if the pointer may be unaligned (which is problematic on the architecture you're supporting), you do not use this one. use iosys_map_memcpy_from instead. not me warning you and then you ignoring me 😭

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🔥 RETURN 🔥

It returns the value read from the mapping. iconic behavior, no notes 👑

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🌈 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_INIT_OFFSET(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_wr(9)
• iosys_map_rd_field(9)
• iosys_map_wr_field(9)

like the whole iosys_map friend group fr fr 💖

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anyway that's the page!! brought to you by ./include/linux, dated October 2026 — mwah, go read some kernel headers, ily, bye 💜🧚