itcw_init(9)

💅 itcw_init(9) — the kernel API glow-up

okay bestie, welcome to itcw_init(9) ✨ this is a page from the Kernel API Manual and it's all about getting your incremental tcw data structure ready to slay. it's in ./drivers/s390/cio if you're wondering where it lives 🎀

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🌸 NAME 🌸

itcw_init — initializes the incremental tcw data structure, no cap 💖

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✨ SYNOPSIS ✨

struct itcw * itcw_init (void *buffer , size_t size , int op , int intrg
, int max_tidaws , int intrg_max_tidaws );

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🦋 ARGUMENTS 🦋

• buffer — the address of the buffer you're gonna use for the data structures 🫶
• size — how many bytes are in that buffer, literally the byte count
• op — pass ITCW_OP_READ if you want a read operation tcw, or ITCW_OP_WRITE if you want a write operation tcw. pick your fighter 💅
• intrg — if this is non-zero, an interrogate tcw gets added and initialized ✨
• max_tidaws — the maximum number of tidaws used for data addressing, or zero if no tida is to be used
• intrg_max_tidaws — the maximum number of tidaws used for data addressing by the interrogate tcw, if one was specified 👑

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💜 DESCRIPTION 💜

so the whole vibe here is: you hand over this buffer and itcw_init preps it to be used as an incremental tcw — which is basically a helper data structure that lets you build a valid tcw through successive calls to other helper functions. teamwork, iykyk 🧚

⚠️ heads up bestie: the buffer needs to be located below the 2G address limit. that's not optional, that's the law 💀

and the resulting tcw comes with these restrictions, fr fr:

• no tccb tidal
• input/output tidal is contiguous (no ttic)
• total data should not exceed 4k
• tcw specifies either read or write operation

on success, it returns a pointer to the resulting incremental tcw data structure. otherwise you get ERR_PTR — not iconic, but that's the deal 🙈

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🔥 SEE ALSO 🔥

Kernel file ./drivers/s390/cio/itcw.c, plus these baddies: itcw_get_tcw(9), itcw_calc_size(9), itcw_add_dcw(9), itcw_add_tidaw(9), itcw_set_data(9), itcw_finalize(9) ⭐

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and that's the whole page, bestie 🎀 mwah 💋

this little love letter comes to you from ./drivers/s390/cio, dated October 2026, and it's your girl itcw_init(9) signing off 🌈💖🦋