Re: [RFC PATCH] dm: add deviceless messages

On Tue, May 12, 2026 at 03:36:01PM +0200, Mikulas Patocka wrote:
> The VDO code needs to perform some calculations before creating a device. 
> The calculations should be performed in the kernel, so that the same logic 
> is not duplicated in the kernel and in the userspace.
> 
> However, currently it is not possible to call a device mapper target 
> when no device exists.
> 
> This commit solves the problem by adding "deviceless" messages. If the 
> message starts with '%', the name is a name of a target, not a name of a 
> device. The message will be directed to the target by calling the 
> "deviceless_message" method. The target can perform the requested 
> calculations in this method and return the result back to userspace.
> 
> Signed-off-by: Mikulas Patocka <[email protected]>

Reviewed-by: Benjamin Marzinski <[email protected]>