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Subject: Re: [PATCH] sh: Avoid using IRQ0 on SH3 and SH4
To:     David Laight <David.Laight@ACULAB.COM>,
        'John Paul Adrian Glaubitz' <glaubitz@physik.fu-berlin.de>,
        Guenter Roeck <linux@roeck-us.net>,
        Sergey Shtylyov <s.shtylyov@omp.ru>,
        Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>,
        "linux-sh@vger.kernel.org" <linux-sh@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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From:   Sergei Shtylyov <sergei.shtylyov@gmail.com>
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Date:   Wed, 12 Jul 2023 11:20:46 +0300
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On 7/12/23 11:12 AM, David Laight wrote:

>> Sent: 09 July 2023 00:13
> ....
>> Looking at arch/sh/boards/mach-r2d/irq.c, there is some IRQ translation going
>> on and maybe that's the part where we need to correct the offset by 16?
> 
> Would it be less problematic to use (say) 16 for IRQ_0
> leaving IRQ_1+ as 1+ ?

   I don't think so.

> At least that would only cause issues for code that needed
> to use IRQ_0.
> 
> (It has to be said that making IRQ 0 invalid seemed wrong
> to me. x86 (IBM PC) gets away with it because IRQ 0 is
> always assigned to platform specific hardware.)

   Not only x86, IIRC.
   Have you seen the commit below?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce753ad1549cbe9ccaea4c06a1f5fa47432c8289

   IOW, try arguing with Linus. :-)

> 	David

MBR, Sergey