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Subject: Re: [PATCH 1/2] staging: brcm80211: removed #ifdef __mips__
From: Michael =?ISO-8859-1?Q?B=FCsch?= <m@bues.ch>
To: Roland Vossen <rvossen@broadcom.com>
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Date: Tue, 19 Apr 2011 15:49:20 +0200
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On Tue, 2011-04-19 at 15:45 +0200, Roland Vossen wrote: 
> Hello guys,
> 
> Greg, please drop this patch set. Rest of this email is FYI only.
> 
> Michael:
> 
> > Are you sure? __mips__ is automagically defined by GCC, if compiling
> > for MIPS. Maybe it should be converted to some CONFIG_... symbol.
> > But removal seems wrong.
> 
> You are right. The majority of the removed #ifdef __mips__ code has to 
> do with write flushing. To accomplish this, it performs a R_REG after a 
> W_REG. I assumed that writeb() and friends guarantee ordering and write 
> flushing, but after some reading I learned that this is not the case.
> 
> I will rework the code and submit a new patch set.
> 
> For some background info: this patch was a reaction on an email from 
> John Linville to us. John wrote:
> 
> <quote>
> I took a quick run through a pull of staging from today.  I made a few
> notes, but a lot of them would seem to relate to the utils stuff you
> mention above.  One general comment would be that there still seems
> to be a lot of MIPS-specific stuff buried in the code, in particular
> a lot of "#ifdef __mips__" stuff that if necessary should at least
> be hidden inside the W_REG macro.
> </quote>

You should probably create a new macro W_REG_FLUSH or something like
that, which enforces ordering by reading back the register, if required.
That avoids ugly #ifdefs in the code.

-- 
Greetings Michael.