Re: [Xen-devel] REST MAINTAINERS feedback requested Was:Re: [PATCH v5 01/28] HYPERCALL_version_op. New hypercall mirroring XENVER_ but sane.

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Konrad Rzeszutek Wilk writes ("Re: REST MAINTAINERS feedback requested Was:Re: 
[Xen-devel] [PATCH v5 01/28] HYPERCALL_version_op. New hypercall mirroring 
XENVER_ but sane."):
> On Mon, Apr 11, 2016 at 11:50:25AM +0100, Ian Jackson wrote:
> > I don't think I would be content with simply adding a new sub-op with
> > bigger fixed-length fields.
> 
> It was variable-ish.
...
> /* Return value is the number of bytes written, or XEN_Exx on error.
>  * Calling with empty parameter returns the size of build_id. */
...
> #define XENVER_build_id 10
> struct xen_build_id {
>         uint32_t        len; /* IN: size of buf[]. */
> #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
>         unsigned char   buf[];

This is pretty ugly but tolerable.

The comment introducing the new HYPERCALL_version_op mentions some
other differences with HYPERCALL_xen_version, which seem to suggest
other deficiencies in the latter.  Those deficiencies, together with
the ugliness of the above, would tend to suggest to me that a cleaner
new interface is warranted.

But to an extent some of this conversation seems to be on matters of
taste.

Jan, what is the downside of introducing a new hypercall ?

Ian.

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