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DESCRIPTION

The AGP chipset is positioned between the PCI-Host bridge and the graphics accelerator to provide a high-performance dedicated graphics bus for moving large amounts of data directly from host memory to the graphics accelerator. The specification currently supports a peak bandwidth of 528 MB/s. AGP uses a Graphics Address Remapping Table (GART) to provide a physically-contiguous view of scattered pages in host memory for DMA transfers.

The agp driver supports the following chipsets:

• ALI M1541 host-to-AGP bridge
• AMD 751 and 761 host-to-AGP bridges
• Intel 82810, 82810-DC100, 82810E, and 82815 SVGA controllers
• SiS 5591 host-to-AGP bridge
• VIA

The agp driver also provides an interface to user processes for use by X servers. A user process communicates to the device initially by means of ioctl(2) calls. The calls supported are:

AGPIOC_INFO

Get AGP information, setting the members in the agp_info structure as defined in <sys/agpio.h>:

typedef struct _agp_info {
        agp_version version;    /* version of the driver        */
        uint32_t bridge_id;     /* bridge vendor/device         */
        uint32_t agp_mode;      /* mode info of bridge          */
        off_t aper_base;        /* base of aperture             */
        size_t aper_size;       /* size of aperture             */
        size_t pg_total;        /* max pages (swap + system)    */
        size_t pg_system;       /* max pages (system)           */
        size_t pg_used;         /* current pages used           */
} agp_info;

AGPIOC_ACQUIRE

Acquire AGP.

AGPIOC_RELEASE

Release AGP.

AGPIOC_SETUP

Set up AGP, using the members in the agp_setup structure as defined in <sys/agpio.h>:

typedef struct _agp_setup {
        uint32_t agp_mode;      /* mode info of bridge          */
} agp_setup;

AGPIOC_ALLOCATE

Allocate AGP space, using and setting the members in the agp_allocate structure as defined in <sys/agpio.h>:

typedef struct _agp_allocate {
        int key;                /* tag of allocation            */
        size_t pg_count;        /* number of pages              */
        uint32_t type;          /* 0 == normal, other devspec   */
        uint32_t physical;      /* device specific (some devices
                                 * need a phys address of the
                                 * actual page behind the gatt
                                 * table)                       */
} agp_allocate;

AGPIOC_DEALLOCATE

Deallocate AGP space.

AGPIOC_BIND

Bind AGP space, using the members in the agp_bind structure as defined in <sys/agpio.h>:

typedef struct _agp_bind {
        int key;                /* tag of allocation            */
        off_t pg_start;         /* starting page to populate    */
} agp_bind;

AGPIOC_UNBIND

Unbind AGP space, using the members in the agp_unbind structure as defined in <sys/agpio.h>:

typedef struct _agp_unbind {
        int key;                /* tag of allocation            */
        uint32_t priority;      /* priority for paging out      */
} agp_unbind;

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/agpio.h>
#include <fcntl.h>
#include <err.h>

int
main(int argc, char **argv)
{
	int fd;
	agp_info info;
	agp_allocate alloc;
	agp_setup setup;
	agp_bind bind;
	agp_unbind unbind;

	fd = open("/dev/agp0", O_RDWR);
	if (fd < 0)
		err(1, "open");

	if (ioctl(fd, AGPIOC_INFO, &info) < 0)
		err(2, "ioctl AGPIOC_INFO");

	printf("version:	%u.%u\n", info.version.major,
	    info.version.minor);

	printf("id:		%x\n", info.bridge_id);
	printf("mode:		%x\n", info.agp_mode);
	printf("base:		%x\n", info.aper_base);
	printf("size:		%uM\n", info.aper_size);
	printf("total mem:	%u\n", info.pg_total);
	printf("system mem:	%u\n", info.pg_system);
	printf("used mem:	%u\n\n", info.pg_used);

	setup.agp_mode = info.agp_mode;

	if (ioctl(fd, AGPIOC_SETUP, &setup) < 0)
		err(3, "ioctl AGPIOC_SETUP");

	if (ioctl(fd, AGPIOC_ACQUIRE, 0) < 0)
		err(3, "ioctl AGPIOC_ACQUIRE");

	alloc.type = 0;
	alloc.pg_count = 64;

	if (ioctl(fd, AGPIOC_ALLOCATE, &alloc) < 0)
		err(4, "ioctl AGPIOC_ALLOCATE");

	printf("alloc key %d, paddr %x\n", alloc.key, alloc.physical);
	if (ioctl(fd, AGPIOC_INFO, &info) < 0)
		err(5, "ioctl AGPIOC_INFO");

	bind.key = alloc.key;
	bind.pg_start = 0x1000;

	if (ioctl(fd, AGPIOC_BIND, &bind) < 0)
		err(6, "ioctl AGPIOC_BIND");

	printf("used mem now:	%u\n\n", info.pg_used);

	unbind.key = alloc.key;
	unbind.priority = 0;

	if (ioctl(fd, AGPIOC_UNBIND, &unbind) < 0)
		err(6, "ioctl AGPIOC_BIND");

	if (ioctl(fd, AGPIOC_DEALLOCATE, &alloc.key) < 0)
		err(6, "ioctl AGPIOC_DEALLOCATE");

	if (ioctl(fd, AGPIOC_RELEASE, 0) < 0)
		err(7, "ioctl AGPIOC_RELEASE");

	close(fd);

	printf("agp test successful\n");

	return 0;
}