AGP(4)

NAME
agp - accelerated graphics port driver

SYNOPSIS
agp* at pchb?

DESCRIPTION
The agp driver provides machine-independent support for the accelerated graphics port (AGP) found on many PC-based and PCI systems. The AGP specification was designed by Intel.

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   */
                paddr_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;

FILES
/dev/agp?
    AGP GART device special files
/dev/agpgart
    AGP GART device special file

EXAMPLES
This short code fragment is an example of opening the AGP device and performing some basic operations:

    #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;
    }

SEE ALSO
ioctl(2), pci(4)

HISTORY
The agp driver first appeared in FreeBSD 4.1. It was adopted in NetBSD 1.6.