LPT(4)

📦 version 12.2, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu questing, ubuntu resolute, ubuntu stonking

💖 LPT 💖

ok bestie, buckle up, we're talking about the lpt generic printer device driver, straight out of the Kernel Interfaces Manual. yes it's a manual page, yes it's from 1999, and yes it still ate 💅

✨ NAME ✨

lpt — generic printer device driver 🖨️🌸

🦋 SYNOPSIS 🦋

device ppc
device ppbus
device lpt

three little lines. that's it. that's the whole vibe. ✨

🎀 DESCRIPTION 🎀

okay so the current lpt driver is literally just the port of the original lpt driver over to the ppbus(4) system. a glow-up, if you will. 💅

and why did they do this port, you ask? two reasons, bestie:

  1. it lets the parallel port be shared with other parallel devices (sharing is caring, we love a communal queen 👑)
  2. the inb()/outb() calls got swapped out for ppbus function calls. and now lpt is arch-independent thanks to the ppbus interface. iconic. see ppbus(4) for more info about the whole ppbus system, iykyk.

the parallel port bus gets allocated by lpt when the printer device is opened, and it's released only when the transfer is completed: either when the device is closed, or when the entire buffer is sent in interrupt driven mode. it holds on until it's done, no cap 🫶

the driver can be configured to be either interrupt-driven, or to poll the printer. and here's the cute part — ports that are configured to be interrupt-driven can be switched to polled mode by using the lptcontrol(8) command. slay.

depending on your hardware, extended capabilities may be configured with the lptcontrol(8) command too. with an ECP/ISA port, you can take advantage of FIFO and DMA. fancy. 🔥

and ooh, want printer info from /dev/lpt0? just apply the cat command to the device, literally that's it. if the printer supports IEEE1284 nibble mode and has data to send to the host, you will get it. it's giving instant gratification. 💖

🌸 FILES 🌸

  • /dev/lpt0 — first parallel port driver ⭐

🌈 SEE ALSO 🌈

go read them, bestie, they're all in the group chat 🫶

💜 HISTORY 💜

this driver replaces the functionality of the lpa driver, which is now defunct. lpa didn't make it. we don't talk about lpa. 💀

😭 BUGS 😭

ok so, the tea:

  • there are lots of them. especially in cheap parallel port implementations. (the cheap ones are NOT passing the vibe check 🙈)
  • it is only possible to open a lpt port when a printer is connected and on-line, which makes it impossible to run lptcontrol(8) when there is no printer connected. like, you literally can't. the door is locked and the printer has the key. 😭
  • this driver could still stand a rewrite.
fr fr, that last one is just written in the manual. they said it, not me. 💀

and that's the whole page, bestie!! 🎀 this one came out of the Debian edition, dated February 14, 1999 — a literal Valentine's Day release, which is honestly the most romantic thing a manpage has ever done. happy reading, go cat a printer. 🦋💖✨

📦 where this page comes from