Re: [PATCH v3 04/41] virtio: memory access APIs

[Geert Uytterhoeven]

On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
>> On Mon, Nov 24, 2014 at 12:52 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>> > virtio 1.0 makes all memory structures LE, so
>> > we need APIs to conditionally do a byteswap on BE
>> > architectures.
>> >
>> > To make it easier to check code statically,
>> > add virtio specific types for multi-byte integers
>> > in memory.
>> >
>> > Add low level wrappers that do a byteswap conditionally, these will be
>> > useful e.g. for vhost.  Add high level wrappers that
>> > query device endian-ness and act accordingly.
>>
>> > diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
>> > new file mode 100644
>> > index 0000000..824ed0b
>> > --- /dev/null
>> > +++ b/include/linux/virtio_byteorder.h
>>
>> > +static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
>> > +{
>> > +       if (little_endian)
>> > +               return le16_to_cpu((__force __le16)val);
>> > +       else
>> > +               return (__force u16)val;
>> > +}
>>
>> What's wrong with just using le16-to_cpu() ...
>
> le16-to_cpu() is simply wrong: virtio needs to be
> LE or native endian, depending on whether it's running
> in 0.9 or 1.0 mode.

IC, that was not clear from the description for this patch.
I thought it was dependent on BE architectures.

Nevertheless, any chance you can get rid of the "conditional"?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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