write_wr_hdr_sgl(9)

💅 write_wr_hdr_sgl(9) — the kernel API manual, but make it cute ✨

okay so bestie, listen. this is the write_wr_hdr_sgl manual page from the Kernel API Manual, and it's literally about writing a WR header and, optionally, an SGL. we're in the net driver trenches and it's giving very much "I know what I'm doing" energy. let's get into it 🫶

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🌸 SYNOPSIS 🌸

void write_wr_hdr_sgl (unsigned int ndesc , struct sk_buff *skb , struct
tx_desc *d , unsigned int pidx , const struct sge_txq *q , const struct
sg_ent *sgl , unsigned int flits , unsigned int sgl_flits , unsigned int
gen , __be32 wr_hi , __be32 wr_lo );

that's the whole signature, no cap. memorize it or at least keep it in a pinned tab 💖

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🎀 ARGUMENTS 🎀

• ndesc — how many Tx descriptors the SGL spans. yes, the actual count, be precise bestie 💅
• skb — the packet that corresponds to the WR. it's the main character, give it respect ✨
• d — the first Tx descriptor to be written. this is where the magic starts 🪄
• pidx — the index of those descriptors above. yes, the index. not optional, keep track 🔥
• q — the SGE Tx queue. the whole energy of this operation lives here 👑
• sgl — the SGL itself. the icon, the moment 💫
• flits — number of flits to the start of the SGL in the first descriptor. count them, don't guess 🧚
• sgl_flits — the SGL size in flits. also flits, also matters, we love consistency 🌈
• gen — the Tx descriptor generation. gotta know which generation we're in, iykyk 💜
• wr_hi — top 32 bits of the WR header, based on WR type, big endian. important: big endian, don't @ me 💀
• wr_lo — low 32 bits of the WR header, based on WR type, big endian. same vibe, other half 🍓

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🦋 DESCRIPTION 🦋

so here's the tea: this function writes a work request header and an associated SGL. no biggie, just very important kernel stuff ✨

if the SGL is small enough to fit into one Tx descriptor, it's already been written. so at that point we just need to write the WR header. easy, slay, done 💅

otherwise — and this is the highkey part — we have to distribute the SGL across the number of descriptors it spans. yes, spread it out, because we're not monsters, we're kernel devs 🫶

ngl, this is the kind of function where you really do need to know what you're doing. it's not vibes-only, bestie. but you've got this 💖

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💀 SEE ALSO 💀

okay this list is long, but every single one matters. no skipping, no summarizing, we list them all because that's the assignment. here we go:

Kernel file ./drivers/net/ethernet/chelsio/cxgb3/sge.c and these functions:

refill_rspq(9), need_skb_unmap(9), unmap_skb(9), free_tx_desc(9), reclaim_completed_tx(9), should_restart_tx(9), free_rx_bufs(9), add_one_rx_buf(9), refill_fl(9), recycle_rx_buf(9), alloc_ring(9), t3_reset_qset(9), t3_free_qset(9), init_qset_cntxt(9), sgl_len(9), flits_to_desc(9), get_packet(9), get_packet_pg(9), get_imm_packet(9), calc_tx_descs(9), write_sgl(9), check_ring_tx_db(9), write_tx_pkt_wr(9), t3_eth_xmit(9), write_imm(9), check_desc_avail(9), reclaim_completed_tx_imm(9), ctrl_xmit(9), restart_ctrlq(9), deferred_unmap_destructor(9), write_ofld_wr(9), calc_tx_descs_ofld(9), ofld_xmit(9), restart_offloadq(9), queue_set(9), is_ctrl_pkt(9), t3_offload_tx(9), offload_enqueue(9), deliver_partial_bundle(9), ofld_poll(9), rx_offload(9), restart_tx(9), cxgb3_arp_process(9), rx_eth(9), lro_add_page(9), handle_rsp_cntrl_info(9), check_ring_db(9), is_new_response(9), process_responses(9), napi_rx_handler(9), process_pure_responses(9), handle_responses(9), t3_intr_handler(9), t3_sge_err_intr_handler(9), sge_timer_tx, sge_timer_rx(9), t3_update_qset_coalesce(9), t3_sge_alloc_qset(9), t3_start_sge_timers(9), t3_stop_sge_timers(9), t3_free_sge_resources(9), t3_sge_start(9), t3_sge_stop_dma(9), t3_sge_stop(9), t3_sge_init(9), t3_sge_prep(9)

that's the whole friend group, go say hi 😭🌸

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🌟 little sign-off 🌟

this page lives in ./drivers/net/ethernet/chelsio..., it's dated October 2026, and it's part of the write_wr_hdr_sgl(9) manual. stay hydrated, read your man pages, and remember: every detail matters, even the flits 💖✨🎀