cma_declare_contiguous_nid(9)

💅 cma_declare_contiguous_nid(9) 💅

okay so this is a page straight out of the Kernel API Manual, and it's literally about carving out your own custom contiguous memory area. bestie, it's giving "I made this block myself" energy 🎀

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✨ NAME ✨

cma_declare_contiguous_nid — reserve custom contiguous area 🫶

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🌸 SYNOPSIS 🌸

int cma_declare_contiguous_nid (phys_addr_t base , phys_addr_t size ,
phys_addr_t limit , phys_addr_t alignment , unsigned int order_per_bit ,
bool fixed , const char *name , struct cma **res_cma , int nid );

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🦋 ARGUMENTS 🦋

• base — the base address of the reserved area. it's optional, so just use 0 if you want literally any address 💫
• size — the size of the reserved area, in bytes. yes, bytes. no cap 📏
• limit — end address of the reserved memory. also optional, 0 means any 💜
• alignment — alignment for the CMA area. should be a power of 2, or zero. those are your two moods ✨
• order_per_bit — order of pages represented by one bit on the bitmap. that's the whole vibe 🔥
• fixed — a hint about where to place the reserved area. it's hinting, not demanding 👀
• name — the name of the area. see the function cma_init_reserved_mem 🎀
• res_cma — pointer to store the created cma region in. that's where the good stuff lands 📦
• nid — nid of the free area to find, or NUMA_NO_NODE for any node 🌈

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⭐ DESCRIPTION ⭐

so this function reserves memory from the early allocator. and like — timing matters, okay? it should be called by arch specific code once the early allocator (memblock or bootmem) has been activated, and all the other subsystems have already allocated/reserved their memory. everyone else eats first, then you get your plate 🍓

this function is the whole point: it lets you create custom reserved areas. main character energy, honestly 👑

if fixed is true, it reserves the contiguous area at exactly base. if it's false, it reserves in the range from base to limit. that's the difference, and it's iconic 💅

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💀 SEE ALSO 💀

• Kernel file ./mm/cma.c
• cma_init_reserved_mem(9)
• cma_alloc(9)
• cma_release(9)

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okay that's the whole thing, go forth and reserve your memory responsibly 🧚💖

source: ./mm — version vibes: October 2026 🦋✨