Libguestfs - Jan 2018 - Re: [PATCH 4/9] backend: Add a .plugin_name method.

On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:
> This returns the plugin name, which for plugins is the same as the
> ordinary .name method (but for filters will be different).
> ---
Just as .name and .plugin_name can differ for filters, should we also
have a way to report independent version numbers (via .version) for the
filter, compared to the version of the underlying plugin (via
.plugin_version)?
> +++ b/src/plugins.c
> @@ -465,6 +465,7 @@ static struct backend plugin_functions = {
>    .free = plugin_free,
>    .thread_model = plugin_thread_model,
>    .name = plugin_name,
> +  .plugin_name = plugin_name,
>    .usage = plugin_usage,
>    .version = plugin_version,
>    .dump_fields = plugin_dump_fields,
> 
-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

On Wed, Jan 17, 2018 at 04:14:56PM -0600, Eric Blake
wrote:
> On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:
> > This returns the plugin name, which for plugins is the same as the
> > ordinary .name method (but for filters will be different).
> > ---
> 
> Just as .name and .plugin_name can differ for filters, should we also
> have a way to report independent version numbers (via .version) for the
> filter, compared to the version of the underlying plugin (via
> .plugin_version)?
As it currently stands it's not necessary because main.c does:

  if (version) {
    const char *v;
    struct backend *b;

    display_version ();
    for_each_backend (b) {
      printf ("%s", b->name (b));
      if ((v = b->version (b)) != NULL)
        printf (" %s", v);
      printf ("\n");
    }
    exit (EXIT_SUCCESS);
  }

with the output:

$ ./nbdkit --filter offset --filter delay file --version
nbdkit 1.1.26
offset 1.1.26
delay 1.1.26
file 1.1.26

Rich.

-- 
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On 01/18/2018 03:09 AM, Richard W.M. Jones wrote:
> On Wed, Jan 17, 2018 at 04:14:56PM -0600, Eric Blake wrote:
>> On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:
>>> This returns the plugin name, which for plugins is the same as the
>>> ordinary .name method (but for filters will be different).
>>> ---
>>
>> Just as .name and .plugin_name can differ for filters, should we also
>> have a way to report independent version numbers (via .version) for the
>> filter, compared to the version of the underlying plugin (via
>> .plugin_version)?
> 
> As it currently stands it's not necessary because main.c does:
...
> with the output:
> 
> $ ./nbdkit --filter offset --filter delay file --version
> nbdkit 1.1.26
> offset 1.1.26
> delay 1.1.26
> file 1.1.26
And if we argue that filters do not have ABI guarantees, where newer
nbdkit will refuse to run with an older filter file (for fear that the
older filter will not properly munge all the new features supported in
the newer plugin), then the version of filters may be less important
(the filter can't even load if it is not the same ABI version as
supported in the nbdkit version).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org