Comment by zozbot234

Comment by zozbot234 16 hours ago

> In one of my previous adventures, we were asking the operator to put the archival tape back, and then re-issuing the close() syscall, with the driver checking that the tape is inserted and passing the control to the mechanical arm for further positioning of the tape, all of that in the drivers running in the kernel space.

Why can't the OS itself do the prompting in this case, as part of processing the original close()? MS-DOG had its (A)bort/(R)etry/(I)gnore prompt for failing I/O operations, and AmigaOS could track media labels and ask the user to "insert $MEDIA_LABEL in drive".

MrResearcher 16 hours ago

Because DOS relied on BIOS interrupt 10h to handle I/O:

  mov si, GREETINGS_STRING
  print_loop:
    lodsb                  ; Load next byte into AL, advance SI
    cmp al, 0              ; Check for null terminator
    je done

    mov ah, 0Eh            ; BIOS teletype output
    mov bh, 0              ; Page number = 0
    mov bl, 07h            ; Light gray on black in text mode
    int 10h                ; Print character in AL

    jmp print_loop
  done:
    ...

  GREETINGS_STRING db "Hello, BIOS world!", 0

And linux doesn't rely on BIOS for output I/O, it provides TTY subsystem and then programs use devices like /dev/tty for I/O. Run $ lspci in your console: which of those devices should the kernel use for output? The kernel wouldn't know that and BIOS is no longer of any help.

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zozbot234 16 hours ago

> which of those devices should the kernel use for output?
Whatever facility it uses for showing kernel panics, perhaps. Though one could also use IPC facilities such as dbus to issue a prompt in the session of whatever user is currently managing that media device.

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