[gentoo-user] CONFIG_USB_SUSPEND, where ?

[Alain Didierjean]

* Messages for package sys-fs/udisks-1.0.4-r1:

*   CONFIG_USB_SUSPEND:         is not set when it should be.

As the message above from emerge says, no way to update sys-fs/udisks as 
CONFIG_USB_SUSPEND is not set.
The problem is where to find that option. Not in linux/.config, so where ?