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Re: [Qemu-ppc] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv

From: Peter Maydell
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv9 MMU TTE
Date: Fri, 16 Aug 2019 13:02:03 +0100

On Fri, 16 Aug 2019 at 12:37, <address@hidden> wrote:
> Hi Phillippe,
> On 8/16/19 7:58 PM, Philippe Mathieu-Daudé wrote:
> >On 8/16/19 8:28 AM, address@hidden wrote:
> >> For each device declared with DEVICE_NATIVE_ENDIAN, find the set of
> >> targets from the set of target/hw/*/device.o.
> >>
> >> If the set of targets are all little or all big endian, re-declare
> >> the device endianness as DEVICE_LITTLE_ENDIAN or DEVICE_BIG_ENDIAN
> >> respectively.
> >
> >If only little endian targets use a device, that doesn't mean the device
> >is designed in little endian...
> >
> >Then if a big endian target plan to use this device, it will require
> >more work and you might have introduced regressions...
> >
> >I'm not sure this is a safe move.
> >
> >> This *naive* deduction may result in genuinely native endian devices
> >> being incorrectly declared as little or big endian, but should not
> >> introduce regressions for current targets.
> >
> Roger. Evidently too naive. TBH, most devices I've never heard of...

OTOH it's worth noting that it's quite likely that most of
the implementations of these DEVICE_NATIVE_ENDIAN devices
picked it in an equally naive way, by just copying some other
device's code...

-- PMM

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