Re: [PATCH v11 2/2] docs: qcow2: introduce compression type feature

[Eric Blake]

On 1/31/20 11:34 AM, Alberto Garcia wrote:
> On Fri 31 Jan 2020 03:46:12 PM CET, Eric Blake wrote:
> > > +                    If the incompatible bit "Compression type" is set: the 
> > > field
> > > +                    must be present and non-zero (which means non-zlib
> > > +                    compression type). Otherwise, this field must not be 
> > > present
> > > +                    or must be zero (which means zlib).
> >
> >              If the incompatible bit "Compression type" is set: the field
> >              must be present. Otherwise, this field must not be present
> >              or must be zero (which means zlib).
>
> But "not being present" and "being zero" is equivalent (as described in
> the previous commit).
>
> And if the incompatible bit is not present then the field can be safely
> ignored (i.e. whether it is zero or not is irrelevant).
>
> Let's try again:
>
>     Defines the compression method used for compressed clusters. All
>     compressed clusters in an image use the same type.
>
>     The value of this field should only be used when the incompatible bit
>     "Compression type" is set. If that bit is unset then this field is
>     not used and the compression method is zlib.

I like that wording.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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