tccb_add_dcw(9)

tccb_add_dcw(9) — Kernel API Manual ✨

okay so bestie, welcome to the tccb_add_dcw(9) page from the Kernel API Manual 💖 this is the lil function that adds a dcw to the tccb, and yes it's giving kernel-internals main character energy. iykyk 🫶

💖 NAME 💖

tccb_add_dcw — add a dcw to the tccb 🌸

✨ SYNOPSIS ✨

struct dcw * tccb_add_dcw (struct tccb *tccb , size_t tccb_size , u8 cmd , u8 flags , void *cd , u8 cd_count , u32 count );

🌸 ARGUMENTS 🌸

• tccb — the tccb address 📍
• tccb_size — the maximum tccb size 📏
• cmd — the dcw command 🕹️
• flags — flags for the dcw 🚩
• cd — pointer to control data for this dcw or NULL if none is required 🫶
• cd_count — number of control data bytes for this dcw 🔢
• count — number of data bytes for this dcw 🧮

🦋 DESCRIPTION 🦋

So basically: add a new dcw to the specified tccb by writing the dcw information specified by cmd, flags, cd, cd_count and count to the tca of the tccb ✨. On success you get a pointer to the newly added dcw back — slay 💅. If the new dcw would exceed the available space as defined by tccb_size, you get -ENOSPC instead 😭. That's the vibe check: fits = pointer, doesn't fit = -ENOSPC.

🎀 NOTE 🎀

Heads up bestie: the tcal field of the tccb header will be updates to reflect added content 🎀.

🌈 SEE ALSO 🌈

• Kernel file ./drivers/s390/cio/fcx.c 📁
• tcw_get_intrg(9)
• tcw_get_data(9)
• tcw_get_tccb(9)
• tcw_get_tsb(9)
• tcw_init(9)
• tcw_finalize(9)
• tcw_set_intrg(9)
• tcw_set_data(9)
• tcw_set_tccb(9)
• tcw_set_tsb(9)
• tccb_init(9)
• tsb_init(9)
• tcw_add_tidaw(9)

xoxo, your kernel bestie 💖 — source/version ./drivers/s390/cio, dated October 2026. mwah 💋