Re: [Qemu-devel] [PATCH v2 3/3] qemu-img: Document backing options

[Max Reitz]

On 28.04.2017 11:38, Kevin Wolf wrote:
> Am 27.04.2017 um 17:36 hat Eric Blake geschrieben:
>> On 04/26/2017 08:46 AM, Max Reitz wrote:
>>> I think originally the idea was to remove the individual special case
>>> options in the long term in favour of the uniform -o. But I don't think
>>> the short options have fallen out of use, so we can as well document
>>> them again...

Hm, I'm not really sure what the use of deprecating them would be. We
would be able to use the single-letter options -b/-B/-F for something
else, but would we really want to do that...?

(And it should always be trivial to map these legacy parameters to
normal options.)

>>> Maybe we could change the implementation, however, so that the old
>>> options are really just aliases for the respective -o version.
>>
>> As in, a followup patch that adds a paragraph or two to the .texi file
>> stating that '-B @var{backing_file}' is shorthand for '-o
>> address@hidden'?
> 
> First and foremost, I meant in the C code where we have separate
> variables for all the shorthand options and then need to handle both
> ways explicitly in the code further down. Instead, -B could just
> directly add a 'backing_file' key to a QemuOpts (and -o would do the
> same instead of building a string that is parsed only later).

We already do that more or less for convert, actually (for -B, that is,
not for -o). We just have to keep out_baseimg separately because we
won't have a QemuOpts with -n.

Using add_old_style_options() in img_create() should be easy enough.

> But the documentation change that you're suggesting is probably a good
> idea as well.

Well, I more or less deliberately did not really document -b/-B/-F. I
just documented them in the syntax overview and named the parameters
backing_file and backing_fmt, both of which are valid options and are
*as such* documented in the explanatory text. So from my point of view,
it's already documented to be a shorthand.

Max

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