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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 9 Apr 2015 10:04:39 +0100
Message-ID: <CAFEAcA-PCLk8V5AotARBYc=trCUs-_r92ECpPnjcQpzzi8vr8w@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [Qemu-devel] [PATCH 01/14] memory: Define API for
 MemoryRegionOps to take attrs and return status
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To: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>, Patch Tracking <patches@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Greg Bellows <greg.bellows@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?B?QWxleCBCZW5uw6ll?= <alex.bennee@linaro.org>, Richard Henderson <rth@twiddle.net>

On 9 April 2015 at 09:55, Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:
> Did you consider using a struct here?
> e.g:
>
> typedef struct MemTxAttrs {
>     unsigned int secure : 1;
>     unsigned int master_id : 10;
>     unsigned int etc : 1;
> } MemTxAttrs;
>
> I think you could still pass it by value and my understanding is
> that the compiler will generate similar code.

We discussed this last time round, I think. Whether structs get
passed in registers depends on the host CPU ABI/calling convention.

> I find it more readable, you ca go:
>
> attrs.secure = 1;
> attrs.master_id = 0x77;
> if (!attrs.secure)
>
> instead of:
>
> attrs |= MEMTXATTRS_SECURE
> if (!(attrs & MEMTXATTRS_SECURE))
>
> etc...
>
> Or do you see any disadvantages with this?

I prefer the traditional integer-and-bitops approach, then you
know what you're getting everywhere...

-- PMM