Re: [Xen-devel] [PATCH 4 of 5] blkif.h: Document the RedHat and Citrix blkif multi-page ring extensions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.02.12 at 15:58, Justin Gibbs <justing@xxxxxxxxxxxxxxxx> wrote:
> On Feb 3, 2012, at 6:33 AM, Jan Beulich wrote:
> 
>>>>> On 03.02.12 at 06:24, "Justin T. Gibbs" <justing@xxxxxxxxxxxxxxxx> wrote:
>>> @@ -187,6 +216,25 @@
>>>  *      The machine ABI rules governing the format of all ring request and
>>>  *      response structures.
>>>  *
>>> + * ring-page-order
>>> + *      Values:         <uint32_t>
>>> + *      Default Value:  0
>>> + *      Maximum Value:  MAX(ffs(max-ring-pages) - 1, max-ring-page-order)
>> 
>> Why not just max-ring-page-order. After all, the value is meaningless
>> for a backend that only exposes max-ring-pages.
>> 
>>> + *      Notes:          1, 3
>>> + *
>>> + *      The size of the frontend allocated request ring buffer in units
>>> + *      of lb(machine pages). (e.g. 0 == 1 page, 1 = 2 pages, 2 == 4 pages,
>>> + *      etc.).
>>> + *
>>> + * ring-pages
>>> + *      Values:         <uint32_t>
>>> + *      Default Value:  1
>>> + *      Maximum Value:  MAX(max-ring-pages,(0x1 << max-ring-page-order))
>> 
>> Similarly here - just max-ring-pages should do.
> 
> This patch documents existing extensions.  For a new driver to properly 
> negotiate a
> multi-page ring with a Dom0 on EC2 (ring-pages) or a Citrix Dom0/guest 
> (ring-page-order),
> you must use the XenBus node names as I've defined them here.

That wasn't my point. I was exclusively asking the maximum values to
get simplified.

Jan


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