BUS_ACTIVATE_RESOURCE(9)

💅 BUS_ACTIVATE_RESOURCE(9) — the manual page, but make it make sense 💅

okay so bestie, welcome to the BUS_ACTIVATE_RESOURCE(9) manual page from the Kernel Developer's Manual. This is the whole vibe: two functions that flip a resource on and off, plus all the lore you need to not fumble it. periodt ✨

✨ NAME ✨

bus_activate_resource, bus_deactivate_resource — activate or deactivate a resource. that's the whole name tea 🎀

🎀 SYNOPSIS 🎀

bestie, copy these includes exactly, no cap:

#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 💖

okay so these functions activate or deactivate a previously allocated resource. In general (lowkey), 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, bestie:

• dev — The device that requests ownership of the resource. Before allocation, the resource is owned by the parent bus. so it's giving main character device energy
• 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). iykyk

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). not me trying to be independent but okay

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(). highkey, the wrapper API is preferred in new drivers. slay

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. fr fr, zero is the bestie we want, any error is the ick 💀

🔥 SEE ALSO 🔥

go read these next, no cap:

• 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>. ngl, iconic behavior 👑

okay bestie, that's the whole page! This one came from Debian, dated May 20, 2016, and it's literally BUS_ACTIVATE_RESOURCE(9). bye mwah 💖✨