Re: [Qemu-devel] [PATCH] block: prefer protocol_name over format_name in bdrv_iterate_format

[Kevin Wolf]

Am 15.04.2014 um 15:28 hat Jeff Cody geschrieben:
> Some block drivers have multiple BlockDriver instances with identical
> format_name fields (e.g. gluster, nbd).  In those cases, the
> protocol_name is usually the more unique identifier (e.g. gluster+tcp).
> 
> Both qemu-img and qemu will use bdrv_iterate_format() to list the
> supported formats when a help option is invoked.  When just the
> format_name is used, redundant listings of formats occur (e.g.,
> "Supported formats: ... gluster gluster gluster gluster ... ").
> 
> If we prefer the protocol_name over the format_name (when the
> protocol name exists), then that provides a more informative
> help message:
> 
> "Supported formats: ... gluster gluster+tcp gluster+unix
> gluster+rdma ... "
> 
> Signed-off-by: Jeff Cody <address@hidden>

On the other hand, it means that you can't take any driver name from
here as use it as -drive driver=... value any more.

The good thing is that most drivers stay in the list, so if anyone was
checking the list to query whether a given driver can be used, it would
still work after this patch. gluster/nbd/sheepdog all have a BlockDriver
with a plain gluster/nbd/sheepdog protocol_name.

The one driver that may cause trouble is vvfat, which would be changed
to fat in the output. Not sure if we care.

Let's wait a bit for more comments on this change before we apply it.
I'm not against it per se, but it's not obviously good either.

Kevin