Re: [Qemu-devel] [PATCH for-1.4] libi2c-omap: Fix endianness dependency

[Peter Maydell <peter.maydell@linaro.org>]

On 2 February 2013 17:37, Andreas Färber <afaerber@suse.de> wrote:
> Am 02.02.2013 17:49, schrieb Peter Maydell:
>> There's nothing special about the OMAP i2c device that I know of:
>> shouldn't the test code just be using a generic "write 16 bit value
>> to memory with appropriate endianness for target CPU" function ?
>
> I asked about where to address this issue [1], no concrete answers, and
> this is the only solution I came up with.
>
> libqtest.h has no generic endian-aware memread functions unlike Alex,
> you or me expected. It reads a sequence of bytes from guest memory and
> transmits them one-by-one over the text-based qtest protocol.

OK, so this is just busted for accessing devices. The protocol
has to have some way of letting you do a 32 bit / 16 bit / 8 bit
access (and maybe 64 bit as well while we're here). memread
and memwrite are OK for RAM accesses [ie anything you'd be
happy to have cached or buffered in a real system] but for
memory mapped registers we need to have an equivalent of
inb/inw/inl/outb/outw/outl that guarantee to do exactly one
access of exactly the required width.

(If you want to do a workaround for 1.4 to get the test suite
running again I don't object; this is just a discussion about
what the right long term fix should be.)

-- PMM