From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: cocci@systeme.lip6.fr
Subject: Re: coccinelle and bitmask arithmetic
Date: Wed, 30 Jan 2013 11:14:20 +0000 [thread overview]
Message-ID: <20130130111420.GG23505@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <5108D808.6010405@bfs.de>
On Wed, Jan 30, 2013 at 09:21:28AM +0100, walter harms wrote:
> Great hit Joe :)
>
> Sometimes i am really surprised what code can be found
> in the kernal and it is still working.
> Having no clue of the code i suspect somebody tries to
> check is mask outside the range it should read
> PHYS_OFFSET |( SZ_64M - 1)
> maybe someone should tell them that
> 1+1\x10 while 1|1=1
> It does not seem to matter here (or ... ?)
This PCI host is only used on one platform (ARMCORE).
For this, PHYS_OFFSET will be a value with only the top few bits of a
32-bit word set (such as 0xc0000000) - it's certainly not going to have
any bits set below bit 26 on the platform this driver gets used on.
"SZ_64M - 1" is the size of the window that RAM appears.
So, _either_ logical OR or addition works.
If we _did_ end up with a PHYS_OFFSET with bits less than bit 26 set
here, we'd have bigger problems - because the base of RAM in PCI space
will not correspond with PHYS_OFFSET and all the DMA mapping stuff breaks.
next prev parent reply other threads:[~2013-01-30 11:14 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-27 19:40 [patch] TTY: synclink, small cleanup in dtr_rts() Dan Carpenter
2013-01-27 20:04 ` Joe Perches
2013-01-27 20:16 ` Jiri Slaby
2013-01-27 20:19 ` Dan Carpenter
2013-01-27 21:00 ` Joe Perches
[not found] ` <C8AFB2C4-4974-4265-A41C-A56C71784F39@microgate.com>
2013-01-28 2:21 ` [PATCH] TTY: synclink: Convert + to | for bit operations Joe Perches
2013-01-28 12:06 ` [patch] TTY: synclink, small cleanup in dtr_rts() walter harms
2013-01-29 15:55 ` Valdis.Kletnieks
2013-01-29 16:13 ` coccinelle and bitmask arithmetic (was: Re: [patch] TTY: synclink, small cleanup in dtr_rts()) Joe Perches
2013-01-29 16:19 ` Julia Lawall
2013-01-29 16:31 ` Joe Perches
[not found] ` <20130129173004.GP16282@mwanda>
2013-01-29 17:42 ` Dan Carpenter
2013-01-29 17:49 ` Julia Lawall
2013-01-29 18:03 ` Joe Perches
2013-01-30 8:21 ` coccinelle and bitmask arithmetic walter harms
2013-01-30 8:29 ` Joe Perches
2013-01-30 11:14 ` Russell King - ARM Linux [this message]
2013-01-30 11:21 ` Julia Lawall
2013-01-30 11:35 ` Russell King - ARM Linux
2013-01-30 16:53 ` Joe Perches
2013-01-30 18:23 ` Russell King - ARM Linux
2013-01-29 18:38 ` coccinelle and bitmask arithmetic (was: Re: [patch] TTY: synclink, small cleanup in dtr_rts()) Julia Lawall
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