vme_master_rmw(9)

💅 vme_master_rmw — the vme_master_rmw(9) glow-up

okay so bestie, gather round, because today we're learning about vme_master_rmw(9) from the Kernel API Manual and honestly? she's a lil baddie with a very specific job. no cap. 🎀

---

✨ NAME ✨

vme_master_rmw — perform a read-modify-write cycle. that's it, that's the whole vibe. 🦋

---

🌸 SYNOPSIS 🌸

unsigned int vme_master_rmw (struct vme_resource *resource , unsigned
int mask , unsigned int compare , unsigned int swap , loff_t offset );

like, look at her. five arguments, one unsigned int coming back. main character energy fr fr. 👑

---

🎀 ARGUMENTS 🎀

• resource — pointer to the VME master resource. she's the one holding the keys, so pls make sure it's actually a VME master resource (more on that in RETURN, bestie 😭).
• mask — the bits that get compared and swapped in this whole operation. think of it as the guest list: only these bits are even invited to the party.
• compare — the bits that get compared against the data read from offset. this is the ~reference photo~ your bits have to match.
• swap — the bits that get swapped in the data read from offset. this is the glow-up that actually happens.
• offset — offset into the VME master window where we're doing the whole operation. yes, exactly there. no, not there. there. 💅

---

🦋 DESCRIPTION 🦋

okay so the way this works is: it performs a read-modify-write cycle on the provided location. and the little four-step choreography is:

• first, the location on the VME bus is read. ⭐
• then, the bits selected by mask are compared with compare. vibe check on the bits.
• then — and this is the iconic part — where a selected bit matches that in compare and those bits are selected in swap, the bit gets swapped. 🔥
• finally, the result is written back to the location on the VME bus. slay, we're done here. 💖

like, it's giving read. compare. swap. write. in that order. every single time. periodt.

---

💜 RETURN 💜

• Bytes written on success. we love a win. 🌈
• -EINVAL if resource is not a VME master resource, or if the RMW operation is not supported. so like... check your resource first, bestie, or you're gonna have a bad time. 🙈
• Hardware specific errors may also be returned. yeah. those exist. not our department. 💀

---

💀 SEE ALSO 💀

kernel file ./drivers/staging/vme_user/vme.c — and yes, the whole friend group is here, say hi:

• vme_alloc_consistent(9)
• vme_free_consistent(9)
• vme_get_size(9)
• vme_slave_request(9)
• vme_slave_set(9)
• vme_slave_get(9)
• vme_slave_free(9)
• vme_master_request(9)
• vme_master_set(9)
• vme_master_get(9)
• vme_master_read(9)
• vme_master_write(9)
• vme_master_mmap_prepare(9)
• vme_master_free(9)
• vme_dma_request(9)
• vme_new_dma_list(9)
• vme_dma_pattern_attribute(9)
• vme_dma_pci_attribute(9)
• vme_dma_vme_attribute(9)
• vme_dma_free_attribute(9)
• vme_dma_list_add(9)
• vme_dma_list_exec(9)
• vme_dma_list_free(9)
• vme_dma_free(9)
• vme_irq_request(9)
• vme_irq_free(9)
• vme_irq_generate(9)
• vme_lm_request(9)
• vme_lm_count(9)
• vme_lm_set(9)
• vme_lm_get(9)
• vme_lm_attach(9)
• vme_lm_detach(9)
• vme_lm_free(9)
• vme_slot_num(9)
• vme_bus_num(9)
• vme_register_driver(9)
• vme_unregister_driver(9)

---

and that's the whole page, bestie 💖 this cutie lives under ./drivers/staging/vme_user, and the page dates to October 2026 — vme_master_rmw(9), forever and always. iykyk 🫶✨