From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "Marc-François LUCCA-DANIAU" <mfld.fr@gmail.com>
Cc: ELKS <Linux-8086@vger.kernel.org>
Subject: Re: New feature: a "poweroff" command
Date: Thu, 26 May 2016 13:21:45 +0100 [thread overview]
Message-ID: <20160526132145.2a246c68@www.etchedpixels.co.uk> (raw)
In-Reply-To: <CACpuWU=_fpXOhhGJWWJTr19UAnVTQMT-e80z3Thap2KOc+aKAw@mail.gmail.com>
> This is why, in such situation, if Jody's adds invocation of the BIOS
> 15h in ELKS, it should be surrounded by a configuration option,
> otherwise I would have to add an INT 15h handler in the Flash to
> return CF=1.
That ought to be the behaviour of any even ancient PC class system when
given an INT15 it doesn't know. The APM specification also has some
fairly robust checks to cope with cases it doesn't.
You call the interrupt with
AH = 53 AL = 0
BX = 0
and it's only assumed present if the return is
Carry clear
AH > 0
BH = 'P'
BL = 'M'
so should never be fooled
INT15 returning carry set should also be very safe even on ancient DOS
systems as the INT15 multiplexor is used by DOS itself from at least DOS
3.0 and other OS expect INT 15 0x80 and friends going back to PC/XT.
Alan
prev parent reply other threads:[~2016-05-26 12:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 1:51 New feature: a "poweroff" command Jody Bruchon
[not found] ` <CACpuWUkhdKqRvae7NiY9rDTMzpnv_Qxaftp3FpPcBEDsfppWLw@mail.gmail.com>
2016-05-26 9:31 ` Fwd: " Marc-François LUCCA-DANIAU
[not found] ` <CAMKR1yvd_Ce+ARQbt1yQbZbLjBp039c=b1KH-C6_8GP8TzQRHg@mail.gmail.com>
[not found] ` <CACpuWU=KnPFMTo5QR9c+WYVsKuziVOpNtqY+ae99h2tt=iP_uQ@mail.gmail.com>
2016-05-26 12:02 ` Fwd: " Marc-François LUCCA-DANIAU
2016-05-26 12:12 ` Jody Bruchon
2016-05-26 12:21 ` Alan Cox [this message]
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