sgl_len(9)

💅 sgl_len — a Gen Z girl's guide to the kernel API manual, bestie ✨

okay so real talk, this is a page from the Kernel API Manual (that's the manual name, iykyk 🫶), and it's about one tiny little function that does one tiny little math thing. but we're gonna understand it properly, because that's just how we are. 🌸

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✨ NAME ✨

sgl_len — lowkey just calculates the size of an SGL of the given capacity, and honestly? that's the whole vibe. 💅

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🦋 SYNOPSIS 🦋

unsigned int sgl_len (unsigned int n );

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🎀 ARGUMENTS 🎀

• n — the number of SGL entries. that's it. that's the whole argument bestie, she's a simple queen 👑

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🌈 DESCRIPTION 🌈

okay so here's the tea, no cap: sgl_len calculates the number of flits needed for a Direct Scatter/Gather List that can hold the given number of entries. 🧚

and a flit, before you even ask, is an 8-byte unit. literally eight bytes. that's the unit of measurement. periodt. ⭐

so like… you give it n (how many entries your SGL needs to hold), it hands back how many 8-byte units of space the Direct Scatter/Gather List is gonna take up. it's giving capacity planning main character energy. 💖

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👑 SEE ALSO 👑

honey. buckle up. 🍓

first up, the kernel file this whole thing lives near:

Kernel file ./drivers/net/ethernet/chelsio/cxgb4vf/sge.c

and then the entire friend group, every single one, in order, don't skip a single bestie 😭:

• get_buf_addr(9)
• is_buf_mapped(9)
• need_skb_unmap(9)
• txq_avail(9)
• fl_cap(9)
• fl_starving(9)
• map_skb(9)
• free_tx_desc(9)
• reclaim_completed_tx(9)
• get_buf_size(9)
• free_rx_bufs(9)
• unmap_rx_buf(9)
• ring_fl_db(9)
• set_rx_sw_desc(9)
• refill_fl(9)
• alloc_ring(9)
• flits_to_desc(9)
• is_eth_imm(9)
• calc_tx_flits(9)
• write_sgl(9)
• ring_tx_db(9)
• inline_tx_skb(9)
• t4vf_eth_xmit(9)
• copy_frags(9)
• t4vf_pktgl_to_skb(9)
• t4vf_pktgl_free(9)
• do_gro(9)
• t4vf_ethrx_handler(9)
• is_new_response(9)
• restore_rx_bufs(9)
• rspq_next(9)
• process_responses(9)
• napi_rx_handler(9)
• t4vf_intr_handler(9)
• sge_rx_timer_cb(9)
• sge_tx_timer_cb(9)
• bar2_address(9)
• t4vf_sge_alloc_rxq(9)
• t4vf_sge_alloc_eth_txq(9)
• t4vf_free_sge_resources(9)
• t4vf_sge_start(9)
• t4vf_sge_stop(9)
• t4vf_sge_init(9)

like… that's 43 functions. forty-three. an entire friend group chat and they ALL ate. 🔥

ngl if you're reading this page to understand one of those you're already in the cxgb4vf/sge.c cinematic universe, so maybe just go read the file too. kudos to whoever kept this index this tidy though, fr fr 💀

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and that's the page, bestie!! the source line at the bottom is a cute little truncated path — ./drivers/net/ethernet/chelsio... — and the version/date stamp says October 2026, so this manual page is basically from the future and we respect her for it. 🎀✨🫶