Retrieving Driver Soft State Information

A common problem when debugging a driver is retrieving the soft state for a particular driver instance. The soft state is allocated with the ddi_soft_state_zalloc(9F) routine and obtained by drivers using ddi_get_soft_state(9F). If you know the name of the soft state pointer (the first argument to ddi_soft_state_init(9F)), mdb enables you to retrieve the soft state for a particular driver instance using the ::softstate dcmd:

> *bst_state::softstate 0x3
702b7578

In this case, ::softstate is used to fetch the soft state for instance 3 of the bst sample driver. This pointer points to a bst_soft structure used by the driver to track state for this instance.