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Date: Thu, 13 Jan 2011 15:12:47 -0700
From: Warner Losh <imp@bsdimp.com>
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To: Bruce Evans <brde@optusnet.com.au>
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Cc: svn-src-head@FreeBSD.org, Matthew D Fleming <mdf@FreeBSD.org>,
	svn-src-all@FreeBSD.org, src-committers@FreeBSD.org,
	John Baldwin <jhb@FreeBSD.org>
Subject: Re: svn commit: r217330 - head/sys/x86/x86
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On 01/12/2011 17:06, Bruce Evans wrote:
> On Wed, 12 Jan 2011, John Baldwin wrote:
>
>>> Log:
>>>   Fix a brain fart.  Since this file is shared between i386 and 
>>> amd64, a
>>>   bus_size_t may be 32 or 64 bits.  Change the bounce_zone alignment 
>>> field
>>>   to explicitly be 32 bits, as I can't really imagine a DMA device that
>>>   needs anything close to 2GB alignment of data.
>>
>> Hmm, we do have devices with 4GB boundaries though.  I think I'd 
>> prefer it if
>> you instead if you did this:
>>
>> #if defined(amd64) || defined(PAE)
>> #define    SYSCTL_ADD_BUS_SIZE_T        SYSCTL_ADD_UQUAD
>> #else
>> #define    SYSCTL_ADD_BUS_SIZE_T        SYSCTL_ADD_UINT
>> #endif
>>
>> and then just used SYSCTL_ADD_BUS_SIZE_T() in the code so we could 
>> let the
>> members in the bounce zone retain the same types passed to
>> bus_dma_tag_create().
>
> U_LONG should work on all arches.  malloc(9) still uses u_long instead
> of size_t.  This works for scalars even on the recently removed i386's
> with 32-bit longs where u_long is larger than size_t, since larger is
> a fail-safe direction.  This fails for pointers.  Newer parts of malloc()
> and uma are broken unless u_long is the same as uintptr_t, since they
> cast pointers to u_long.  This direction is fail-safe too, but gcc warns
> about it.

u_long doesn't work for N32.  There, the pointers may only be 32-bit, 
but PAs ar 64-bit.  Longs are only 32-bits.

Warner

>
> uquad_t should never be used, like unsigned long long.  Similarly for
> signed types.  Perhaps it could be removed in sysctl interfaces first.
>
> Bruce
>
>
>