linux-kernel - Re: [patch 3/3] x86: io-apic - code style cleaning for setup_IO_APIC

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Message-ID: <20080906193820.GC23729@lenovo>
Date:	Sat, 6 Sep 2008 23:38:20 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Ingo Molnar <mingo@...e.hu>, hpa@...or.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [patch 3/3] x86: io-apic - code style cleaning for
	setup_IO_APIC_irqs

[Yinghai Lu - Sat, Sep 06, 2008 at 12:16:28PM -0700]
| On Sat, Sep 6, 2008 at 12:04 PM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
| > [Maciej W. Rozycki - Sat, Sep 06, 2008 at 07:45:08PM +0100]
| > | On Sat, 6 Sep 2008, Cyrill Gorcunov wrote:
| > |
| > | > Ingo, how about the following approach? We don't introduce new
| > | > functions but rather srink the code by new printout form.
| > |
| > |  Honestly, this one should probably use sprintf() or suchlike to avoid the
| > | mess of printk() calls building a line of output from pieces.  It's quite
| > | easy to calculate here what the maximum size of the buffer required could
| > | be and automatic arrays can have variable size, so no need for the hassle
| > | of heap management.  Calls to printk() without a trailing newline should
| > | be avoided where possible as it messes up logging priority if a message
| > | pops up from an interrupt inbetween.
| > |
| > |   Maciej
| > |
| >
| > The easiest way would be just print this info on separate
| > lines like
| >
| >        IO-APIC (apicid-pin) 1-1 not connected
| >
| > and just drop all this troubles :)
| >
| > I'm not sure how much memory we need for every io-apic
| > pins - iirc there only 32 redirection entry so it could
| > be about 32 bytes from stack would be enough. Will take
| > a look. Thanks Maciej! Ingo?
| 
| no. some system could have 3 or 4 ioapic controller, and every one
| have 24...(like three mcp55/io55)
| 4*24
| 
| or old system have 1 8111 and 7 8132. will have 32 + 7*2*7
| 
| YH
|

Didn't really understand all numbers :)
We have
	24	io-apic route entries
	128	io-apic maximum in quantity

so the worst (hardly possible if ever) is when on last io-apic
all pins are wrong. So for this case we would need

	(3 + 1) * ((10 + 1) + (13 + 1)) = 100

where
	3 - strlen("127") - max io-apic number
	10 - Sum(strlen(0)+...+strlen(9)) - pin numbers
	13 - same sum for two-digit numbers
	+1 number - either "-" sign or " "

100 bytes to print not connected pins. Ugh :-)

		- Cyrill -
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