From: erfarmer201 AT comcast DOT net (Eric Farmer)
Newsgroups: comp.os.msdos.djgpp
Subject: Disable interrupts around _go32_dpmi calls?
Date: 24 Nov 2002 15:13:34 -0800
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hello,

None of the documentation I have seen suggests wrapping cli/sti around
the setting of an interrupt handler using
_go32_dpmi_*_protected_mode_vector.  Is this required, for example in
the following code:

    outportb(com_port + SERIAL_LCR, 0x03);
    outportb(com_port + SERIAL_IER, 0x00);
    while (inportb(com_port + SERIAL_IIR) & 0x01 == 0) {
        // clean out registers
    }
    _go32_dpmi_seginfo old_isr, new_isr;
    _go32_dpmi_get_protected_mode_interrupt_vector(interruptno,
&old_isr);
    new_isr.pm_offset = (int)isr;
    new_isr.pm_selector = _go32_my_cs();
    _go32_dpmi_allocate_iret_wrapper(&new_isr);
    _go32_dpmi_set_protected_mode_interrupt_vector(interruptno,
&new_isr);

It seems to me that interrupts should be disabled for all of this,
both disabling interrupt generation from the hardware device (UART) as
well as setting the interrupt handler.  But I never see cli/sti calls
wrapped around the handler installation code; what is correct?

Thanks,
Eric Farmer