Re: [Xen-devel] [RFC V2] xen: interface: introduce pvclk interface

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.01.16 at 12:40, <van.freenix@xxxxxxxxx> wrote:
> Hi Jan,
> 
> On Wed, Jan 20, 2016 at 03:14:20AM -0700, Jan Beulich wrote:
>>>>> On 20.01.16 at 09:31, <van.freenix@xxxxxxxxx> wrote:
>>> +/*
>>> + * Backend response
>>> + *
>>> + * cmd: command for operation on clk, same with the cmd in request.
>>> + * id: clk id, same with the id in request.
>>> + * success: indicate failure or success for the cmd.
>>> + * rate: clock rate. Used for get rate.
>>> + *
>>> + * cmd and id are filled by backend and passed to frontend to
>>> + * let frontend check whether the response is for the current
>>> + * request or not.
>>> + */
>>> +struct xen_clkif_response {
>>> +   uint32_t cmd;
>>> +   uint32_t id;
>>> +   uint32_t success;
>>> +   uint64_t rate;
>>> +};
>>
>>This isn't 32-/64-bit clean. Question is whether echoing cmd is really
>>needed.
> 
> As Juergen suggested, use a request id. I'll fix this in V3.
> 32-/64-bit unclean, I can not get you here (:

The layout of above structure may end up different for 32- and
64-bit guests, depending on the alignment of uint64_t.

>>And what I'm missing throughout the file is some description of how
>>clock events (interrupts?) are actually meant to make it into the
>>guest.
> 
> I have a simple implementation v1 patch for linux, 
> http://lists.xen.org/archives/html/xen-devel/2016-01/msg01860.html.
> You can see how it works.

No, sorry, that's not the point of the inquiry. It seems to me that
there are more aspects to this interface, not directly related to
the request/reply protocol written down here, which need to be
spelled out event if they don't require any particular definitions
or type declarations.

Jan


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