cmdq_pkt_write_s(9)

💅 cmdq_pkt_write_s — like, the CMDQ packet write_s appender bestie

okay so real talk, this is a page from the Kernel API Manual (yes the (9) section, we love a kernel-internals moment ✨) and it's all about cmdq_pkt_write_s. Buckle up, it's giving "low-level but make it cute".

---

🌸 NAME 🌸

cmdq_pkt_write_s — append a write_s command to the CMDQ packet. that's it, that's the whole personality 🎀

---

✨ SYNOPSIS ✨

int cmdq_pkt_write_s (struct cmdq_pkt *pkt , u16 high_addr_reg_idx , u16
addr_low , u16 src_reg_idx );

literally the whole signature, don't @ me, it returns an int 💖

---

🫶 ARGUMENTS 🫶

• pkt — the CMDQ packet. the main character, the canvas, the whole vibe 🌈
• high_addr_reg_idx — the internal register ID that's holding the high address of pa. yep, it's a u16, and yep, it's an index not an address, lowkey important 👀
• addr_low — the low address of pa. the bottom half of the address situation 💅
• src_reg_idx — the CMDQ internal register ID that caches the source value. so like, where the value's coming from 🦋

---

👑 RETURN 👑

0 for success 🎉 — otherwise the error code gets returned. not zero? not slay. go check that error code bestie 😭

---

🔥 DESCRIPTION 🔥

so the whole point: this supports writing a value to a physical address without subsys. no subsys needed, we're going direct, main character energy fr fr 💀

here's the little ritual you gotta do tho, don't skip steps:

1. use CMDQ_ADDR_HIGH to get the high address, then call cmdq_pkt_assign to assign that value into an internal reg ✨
2. also use CMDQ_ADDR_LOW to get the low address, and that's what you pass as the addr_low parameter when you call this function 🎀

that's the recipe. high goes through the reg + cmdq_pkt_assign, low goes straight in as addr_low. iconic, honestly 🧚

---

💜 SEE ALSO 💜

kernel file ./include/linux/soc/mediatek/mtk-cmdq.h — go read it, it's the source of truth 📖

and the whole friend group (yes, all of them, no we're not leaving anyone out):

cmdq_dev_get_client_reg(9), cmdq_mbox_create(9), cmdq_mbox_destroy(9), cmdq_pkt_create(9), cmdq_pkt_destroy(9), cmdq_pkt_write(9), cmdq_pkt_write_pa(9), cmdq_pkt_write_subsys(9), cmdq_pkt_write_mask(9), cmdq_pkt_write_mask_pa(9), cmdq_pkt_write_mask_subsys(9), cmdq_pkt_write_s_mask(9), cmdq_pkt_write_s_value(9), cmdq_pkt_write_s_mask_value(9), cmdq_pkt_mem_move(9), cmdq_pkt_wfe(9), cmdq_pkt_acquire_event(9), cmdq_pkt_clear_event(9), cmdq_pkt_set_event(9), cmdq_pkt_poll(9), cmdq_pkt_poll_mask(9), cmdq_pkt_logic_command(9), cmdq_pkt_assign(9), cmdq_pkt_poll_addr(9), cmdq_pkt_jump_abs(9), cmdq_pkt_jump_rel(9), cmdq_pkt_jump_rel_temp(9), cmdq_pkt_eoc(9) 🌟

---

ngl if you got all the way here you're officially a CMDQ girlie now, no cap 🫶

alright that's the page!! it lives at ./include/linux/soc/mediatek, dated October 2026, and the page itself is cmdq_pkt_write_s(9) — mwah, bye bestie 💋💖