spi_mem_dirmap_write(9)

📦 version 7.3.1, in nixpkgs unstable

💅 spi_mem_dirmap_write — the "Kernel API Manual" page, bestie edition 💅

okay so you found yourself staring at spi_mem_dirmap_write(9) and you're like "what does this even do" — don't worry, I got you. This is the <cyan>Kernel API Manual</cyan> entry, and it's genuinely not that deep. It's giving write data through a direct mapping. Slay. ✨

🎀 NAME 🎀

spi_mem_dirmap_write — write data through a direct mapping, no cap 💫

🌸 SYNOPSIS 🌸

ssize_t spi_mem_dirmap_write (struct spi_mem_dirmap_desc *desc , u64
offs , size_t len , const void *buf );

literally that's the whole signature, copy it exactly, don't @ me 🫶

✨ ARGUMENTS ✨

  • desc — the direct mapping descriptor. your little ticket to the mapping, bestie 🎟️
  • offs — offset to start writing from. and listen, this is not an absolute offset — it's the offset within the direct mapping, which already has its own offset. so don't go adding things up in your head, it's already accounted for 🙈
  • len — length in bytes. yes, bytes. the normal unit. 💅
  • buf — the source buffer. this buffer must be DMA-able — like, non-negotiable, fr fr. if it's not DMA-able that's a you problem 💀

💖 DESCRIPTION 💖

so basically this function writes data to a memory device 🌈 using a direct mapping that you already instantiated earlier with spi_mem_dirmap_create. that's it. that's the vibe. it's the write sibling of the read one and it's honestly so iconic for it 👑

lowkey important: the mapping has to exist first. this function doesn't create anything, it just uses what you set up. main character energy but make it a helper function 🧚

⭐ RETURN ⭐

it returns the amount of data written to the memory device, or a negative error code 😭

and here's the part people always miss — the returned size might be smaller than len. not a bug, just how it is. so if that happens, you (yes, you, the caller) are responsible for calling spi_mem_dirmap_write again. keep going until it's all written. it's giving "loop it yourself, bestie" 🔥

🦋 SEE ALSO 🦋

the kernel file lives at ./drivers/spi/spi-mem.c if you wanna go read the source like the icon you are 📖

and here's the whole friend group, all present and accounted for:

go read spi_mem_dirmap_read(9) next, it's the twin, they're adorable together 🫶

okay that's the page!! this was brought to you by the <mint>./drivers/spigirlies, datedOctober 2026` — same energy, same page, see you in the next manpage bestie 💜🎀✨

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