UMCS(4)

📦
version 15.1 · 3 versions
, in freebsd 14.5, freebsd 15.1, nixpkgs unstable

🦋 NAME 🦋

Okay so bestie, meet umcs(4) 💖 — USB support for serial adapters based on the MCS7820 and MCS7840 chips. That’s the name, that’s the vibe, and honestly this driver has main character energy. No cap. ✨

✨ SYNOPSIS ✨

Wanna compile this driver into the kernel? Slay — drop these lines into your kernel configuration file:

device usb
device ucom
device umcs

Or, to load the driver as a module at boot time, put this line in loader.conf(5):

umcs_load="YES"

🌸 DESCRIPTION 🌸

The umcs driver provides support for various multiport serial adapters based on the MosCom MCS7820 and MCS7840 chips. They are 2- or 4-port adapters with full-featured 16550-compatible UARTs and very flexible baud generators. Also, these chips support RS422/RS485 and IrDA operations. Highkey iconic. 🔥

You access the device through the ucom(4) driver, and that’s what makes it behave like a tty(4). Different ports on the device are presented as sub-units, like /dev/ttyU0.1 and /dev/ttyU0.2. It’s giving “one USB situation, multiple little tty besties,” and I’m obsessed. 💅

🔥 HARDWARE 🔥

Vibe check: the umcs driver was tested on these adapters, fr fr:

  • ST Lab U-360 two-port serial USB adapter
  • ST Lab U-400 four-port serial USB adapter

🎀 FILES 🎀

Callin side, coming in hot:

  • /dev/ttyU*.* — for callin ports
  • /dev/ttyU*.*.init
  • /dev/ttyU*.*.lock — corresponding callin initial-state and lock-state devices

Callout side, same energy, iykyk:

  • /dev/cuaU*.* — for callout ports
  • /dev/cuaU*.*.init
  • /dev/cuaU*.*.lock — corresponding callout initial-state and lock-state devices

🦋 SEE ALSO 🦋

Go read these too, bestie:

🌈 HISTORY 🌈

The umcs driver appeared in ports since December of 2010. That’s the lore, periodt. 🫶

👑 AUTHORS 👑

The umcs driver was written by Lev Serebryakov <lev@FreeBSD.org>. Give them their flowers. 💐

💀 BUGS 💀

Real talk, ngl: this driver doesn't support access to any fine tunes of chip, like RS522/RS485 mode, non-standard baudrates, etc. 😭

Cute little sign-off: this page is from Debian, dated April 26, 2017, and filed under UMCS(4). 💖🫶

📦 where this page comes from