TCOM(4)

💅 tcom(4) — the Kernel Interfaces Manual, but make it group chat 🎀

okay so bestie, you know how this is from the Kernel Interfaces Manual section, right? that's the section name, we're keeping it, slay. this page is literally all about tcom and i'm gonna walk you through it 💖

---

✨ NAME ✨

tcom — multiplexing serial communications interface. that's it, that's the whole vibe: it multiplexes serial comms, no cap 🦋

---

🌸 SYNOPSIS 🌸

bestie this part is verbatim, do not touch a single character, i'm serious 🙈

for the 4-port TC-400 series boards:

tcom0 at isa? port 0x100 irq 5
com2 at tcom? slave ?
com3 at tcom? slave ?
com4 at tcom? slave ?
com5 at tcom? slave ?

and for the 8-port TC-800 series boards:

tcom0 at isa? port 0x100 irq 5
com2 at tcom? slave ?
com3 at tcom? slave ?
com4 at tcom? slave ?
com5 at tcom? slave ?
com6 at tcom? slave ?
com7 at tcom? slave ?
com8 at tcom? slave ?
com9 at tcom? slave ?

like, the 8-port one is just the 4-port one but it kept going 💀 iconic behavior honestly.

---

👑 DESCRIPTION 👑

okay so the tcom driver is the main character here: it provides support for the Byte Runner Technologies TC-400 and TC-800 series boards that multiplex together up to four or eight EIA RS-232C (CCITT V.28) communications interfaces. four or eight. EIA RS-232C. CCITT V.28. we love a board with range ✨

each tcom device is the master device for up to eight com devices. yes, master. main character energy fr fr 👑

the kernel configuration specifies these com devices as slave devices of the tcom device, exactly like the synopsis shows. so those slave ? lines? not decoration, bestie, that's the whole point 🫶

here's the tea on how it actually works: the slave ID given for each com device determines which bit in the interrupt multiplexing register is tested to find interrupts for that device. and the port specification for the tcom device is used to compute the base addresses for the com subdevices and the port for the interrupt multiplexing register. literally all connected. iykyk 💅

real talk though: not all possible configuration options are currently supported (for example, speeds beyond 115200 baud are not currently supported). so don't come for this driver with your 200k baud dreams, it's not ready 😭 115200 is the ceiling.

---

🍓 FILES 🍓

• /dev/tty?? — the devices, they live here, periodt 💜

---

🌈 SEE ALSO 🌈

• com(4) — go read that one too, bestie, it's the whole reason tcom has slaves in the first place 🧚

---

⭐ HISTORY ⭐

the tcom driver was written by Jukka Marin. thank you Jukka, we appreciate you 💖

---

and that's the page!! no cap, every detail intact, we did not skip a thing 🌸🦋

this lil number shipped with Debian, dated May 20, 1998 — yes bestie, that's the date on the footer, and yes i'm mentioning it because it deserves its moment 👑✨ mwah, talk later 💅