plucky (9) bus_activate_resource.9freebsd.gz

NAME

     bus_activate_resource, bus_deactivate_resource — activate or deactivate a resource

SYNOPSIS

     #include <sys/param.h>
     #include <sys/bus.h>

     #include <machine/bus.h>
     #include <sys/rman.h>
     #include <machine/resource.h>

     int
     bus_activate_resource(device_t dev, int type, int rid, struct resource *r);

     int
     bus_deactivate_resource(device_t dev, int type, int rid, struct resource *r);

DESCRIPTION

     These functions activate or deactivate a previously allocated resource.  In general, resources must be
     activated before they can be accessed by the driver.  Bus drivers may perform additional actions to ensure
     that the resource is ready to be accessed.  For example, the PCI bus driver enables memory decoding in a
     PCI device's command register when activating a memory resource.

     The arguments are as follows:

     dev     The device that requests ownership of the resource.  Before allocation, the resource is owned by
             the parent bus.

     type    The type of resource you want to allocate.  It is one of:

             PCI_RES_BUS     for PCI bus numbers
             SYS_RES_IRQ     for IRQs
             SYS_RES_DRQ     for ISA DMA lines
             SYS_RES_IOPORT  for I/O ports
             SYS_RES_MEMORY  for I/O memory

     rid     A pointer to a bus specific handle that identifies the resource being allocated.

     r       A pointer to the struct resource returned by bus_alloc_resource(9).

   Resource Mapping
     Resources which can be mapped for CPU access by a bus_space(9) tag and handle will create a mapping of the
     entire resource when activated.  The tag and handle for this mapping are stored in r and can be retrieved
     via rman_get_bustag(9) and rman_get_bushandle(9).  These can be used with the bus_space(9) API to access
     device registers or memory described by r.  If the mapping is associated with a virtual address, the
     virtual address can be retrieved via rman_get_virtual(9).

     This implicit mapping can be disabled by passing the RF_UNMAPPED flag to bus_alloc_resource(9).  A driver
     may use this if it wishes to allocate its own mappings of a resource using bus_map_resource(9).

     A wrapper API for bus_space(9) is also provided that accepts the associated resource as the first argument
     in place of the bus_space(9) tag and handle.  The functions in this wrapper API are named similarly to the
     bus_space(9) API except that “_space” is removed from their name.  For example, bus_read_4() can be used in
     place of bus_space_read_4().  The wrapper API is preferred in new drivers.

     These two statements both read a 32-bit register at the start of a resource:

             bus_space_read_4(rman_get_bustag(res), rman_get_bushandle(res), 0);
             bus_read_4(res, 0);

RETURN VALUES

     Zero is returned on success, otherwise an error is returned.

SEE ALSO

     bus_alloc_resource(9), bus_map_resource(9), bus_space(9), device(9), driver(9)

AUTHORS

     This manual page was written by Warner Losh <imp@FreeBSD.org>.