Re: [Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API

[Kevin Wolf]

Am 13.07.2012 12:55, schrieb Christoph Hellwig:
> On Fri, Jul 13, 2012 at 12:42:41PM +0200, Kevin Wolf wrote:
>> It still feels a bit more like qemu-io-style operations. Not sure what
>> your use case looks like exactly, but adding a qemu-io command that
>> reads data from a file and writes it at a given offset into the images
>> (or vice versa) should be easy. This would be more or less a qemu-dd.
> 
> We already have that if you read/write the whole image, it's called
> qemu-img convert.

Hm. Fair point, I guess. Though qemu-img tends to have commands that
deal with complete disks instead of just areas.

>> If you need to get data from stdin or output it to stdout, then it might
>> not be the right solution.
> 
> That is the use case.  We could appromite it by writing a temp file and
> using qemu-img convert, but that's not very efficient. 

Yeah, it's not what you want then.

So the question is whether to have it integrated in qemu-img or
standalone. I'm undecided: Having everything in one well-known tool has
its advantages. But then, a qemu-dd that feels like a real dd, just that
it opens image formats with the right driver instead of always using
raw, certainly sounds attractive, too.

Let's wait a bit for more opinions. If there aren't any - you write the
code, you decide.

Kevin