linux-kernel - Re: [8259A] Why the irq_desc->handle_irq are set as handle_level_irq() while the ICW1 is set 0x11, which indicates edge mode?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Wed, 11 Jan 2012 23:54:09 +0800
From:	Zhihua Che <zhihua.che@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: [8259A] Why the irq_desc->handle_irq are set as
 handle_level_irq() while the ICW1 is set 0x11, which indicates edge mode?

2012/1/10 Zhihua Che <zhihua.che@...il.com>:
> hi, everyone
>
>      I'm reading kernel codes of version 3.1x and now focusing on
> interrupt subsystem. I find an interesting thing.
>      In x86 architecture, init_8259A() is invoked by init_ISA_irqs()
> to initialize the chip and precisely, the ICW1 of both master and
> slave 8259A chip are set as 0x11 which indicates that the both chip
> are enabled with edge trigger mode. However, I'm wondering why the
> irq_desc->handle_irq fields of the total 16 IRQ descriptor are set as
> handle_level_irq() in init_ISA_irqs(). As far as I know, the
> handle_level_irq() is designed to handle level-mode interrupts.
>      Please Let me know if I miss anything.
>
> Harvey

Precisely,

init_8259A()(int auto_eoi)
{
        *
        *
        *
        outb_pic(0x11, PIC_MASTER_CMD); /* bit3 of ICW1 indicates
trigger mode, here enable edge mode */
        *
        *
}

void init_ISA_irqs(void)
{
        *
        *
        *
        for (i = 0; i < legacy_pic->nr_legacy_irqs; i++)
                 irq_set_chip_and_handler_name(i, chip,
handle_level_irq, name); /* here, handle_level_irq() is intended to
handle edge trigger interrupts */
}

Is this ok?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/