This document contains diagrams and descriptions related to the X Window System architecture for direct and indirect graphics rendering. It shows how OpenGL applications interact with the X server and Mesa library to perform direct graphics rendering using the kernel's Direct Rendering Infrastructure (DRI) and devices' direct rendering capabilities. It also summarizes the DRM authentication process where an application receives a magic cookie from the kernel to authenticate with the DRM driver.

1. X Window / Direct Rendering
Architectural Diagram
Xclient (w/GL)
OpenGL I/F
Xlib I/F Filesystem
libdrm I/F IOCTL / mmap
Driver I/F
Mesa libdrm
PCI
Direct
Xlib Xlib I/F
Driver
Rendering
I/F
Manager
Filesystem
sockets Abstraction
AGP GART
Manager
X protocol Filesystem I/F
Driver I/F Hard-
Kernel
sockets
X Server (device-independent tier) ware
AGP GART
libdrm I/F
XFree86 Tier
Manager
DIX IOCTL / Memory
libdrm
I/F DGA DRI mmap Manager MM
PCI
Subsystem I/F
Driver
vidmode
I/F
Video
XFree86 IOCTL /
IRQ
XAA
PCI Device
Extension mmap
Driver Abstraction IRQM
MI I/F
Manager
I/F
Xv
2007 © Moriyoshi Koizumi. All Rights Reserved.

2. X Window / Indirect Rendering
Architectural Diagram
Xclient (w/GL)
OpenGL I/F
Xlib I/F Filesystem
Driver I/F
Mesa
PCI
Direct
Xlib Xlib I/F
Driver
Rendering
I/F
Manager
Filesystem
sockets Abstraction
AGP GART
Manager
X protocol Filesystem I/F
Driver I/F Hard-
Kernel
sockets
X Server (DIX) ware
GLX Mesa
AGP GART
XFree86 Tier libdrm I/F
Manager
DIX IOCTL / Memory
libdrm
I/F DGA DRI mmap Manager MM
PCI
Subsystem I/F
Driver
vidmode
I/F
Video
XFree86 IOCTL /
IRQ
XAA
PCI Device
Extension mmap
Driver Abstraction IRQM
MI I/F
Manager
I/F
Xv
2007 © Moriyoshi Koizumi. All Rights Reserved.

3. Address Space Layout
Kernel Space
Graphics
MMIO Aperture
Space
Physical
User Space
Address
Space
Actual
RAM
Space
GART
2007 © Moriyoshi Koizumi. All Rights Reserved.

4. Direct Memory Access
1. Queueing
Kernel Space Graphic Controller
Instruction
Buffer DMA FIFO
Transfer
Marked
Consistent IOCTL (BLIT etc.)
User Space
Some
Process
2007 © Moriyoshi Koizumi. All Rights Reserved.

5. Direct Memory Access
2. Bitmap Block Transfer (Blit)
Kernel Space Graphic Controller
Active Entry
FIFO
Parse &
User Space Dispatch
Some
Marked
Process Blit Engine
Consistent
DMA Transfer
Another
Process
2007 © Moriyoshi Koizumi. All Rights Reserved.

6. DRM IOCTL I/F
AUTH (GET_MAGIC / AUTH_MAGIC)
●
VERSION (GET / SET)
●
BUSID (GET / SET)
●
MAP (ADD / RM)
●
CTX (ADD / RM / GET / SWITCH / NEW /
●
RESERVE)
LOCK (LOCK / UNLOCK)
●
AGP operations
●
Device-specific operations
●
2007 © Moriyoshi Koizumi. All Rights Reserved.

7. DRM Authentication
1. Retrieve Magic Cookie (drmGetMagic())
Cookie Manager
Mesa libdrm
2. Generate
Direct
Xlib
Magic
Rendering
Manager Cookie
3. Send Magic
X protocol (XF86DRIAuthConnection()) 4. Authenticate Cookie
(drmAuthMagic())
Kernel
X Server
XFree86 Tier
libdrm
DRI
2007 © Moriyoshi Koizumi. All Rights Reserved.

8. DRM Authentication
(Userland Wrappers)
libdrm/xf86drm.c:
(formally: xc/programs/Xserver/hw/xfree86/os-support/linux/drm/xf86drm.c)
int drmGetMagic(int fd, drm_magic_t * magic)
{
drm_auth_t auth;
*magic = 0;
if (ioctl(fd, DRM_IOCTL_GET_MAGIC, &auth)) return -errno;
*magic = auth.magic;
return 0;
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

9. DRM Authentication
(Userland Wrappers)
xc/programs/Xserver/hw/xfree86/dri/dri.c:
Bool
DRIAuthConnection(ScreenPtr pScreen, drm_magic_t magic)
{
DRIScreenPrivPtr pDRIPriv = DRI_SCREEN_PRIV(pScreen);
if (drmAuthMagic(pDRIPriv->drmFD, magic)) return FALSE;
return TRUE;
}
libdrm/xf86drm.c:
(formally: xc/programs/Xserver/hw/xfree86/os-support/linux/drm/xf86drm.c)
int drmAuthMagic(int fd, drm_magic_t magic)
{
drm_auth_t auth;
auth.magic = magic;
if (ioctl(fd, DRM_IOCTL_AUTH_MAGIC, &auth)) return -errno;
return 0;
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

10. DRM Authentication
(linux/drivers/char/drm/drm_drv.c: IOCTL Dispatch Table)
static drm_ioctl_desc_t drm_ioctls[] = {
[DRM_IOCTL_NR(DRM_IOCTL_VERSION)] = {drm_version, 0},
[DRM_IOCTL_NR(DRM_IOCTL_GET_UNIQUE)] = {drm_getunique,
0},
[DRM_IOCTL_NR(DRM_IOCTL_GET_MAGIC)] = {drm_getmagic, 0},
[DRM_IOCTL_NR(DRM_IOCTL_IRQ_BUSID)] = {drm_irq_by_busid,
DRM_MASTER|DRM_ROOT_ONLY},
[DRM_IOCTL_NR(DRM_IOCTL_GET_MAP)] = {drm_getmap, 0},
[DRM_IOCTL_NR(DRM_IOCTL_GET_CLIENT)] = {drm_getclient,
0},
[DRM_IOCTL_NR(DRM_IOCTL_SET_VERSION)] = {drm_setversion,
DRM_MASTER|DRM_ROOT_ONLY},
[DRM_IOCTL_NR(DRM_IOCTL_AUTH_MAGIC)] = {drm_authmagic,
DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY},
[DRM_IOCTL_NR(DRM_IOCTL_ADD_CTX)] = {drm_addctx,
DRM_AUTH|DRM_ROOT_ONLY},
[DRM_IOCTL_NR(DRM_IOCTL_GET_CTX)] = {drm_getctx,
DRM_AUTH},
...
2007 © Moriyoshi Koizumi. All Rights Reserved.

11. DRM Authentication
(linux/drivers/char/drm/drm_drv.c: IOCTL Dispatcher)
if (nr < DRIVER_IOCTL_COUNT)
ioctl = &drm_ioctls[nr];
else if ((nr >= DRM_COMMAND_BASE)
&& (nr < DRM_COMMAND_BASE + dev->driver->num_ioctls))
ioctl = &dev->driver->ioctls[nr - DRM_COMMAND_BASE];
else
goto err_i1;
func = ioctl->func;
/* is there a local override? */
if ((nr == DRM_IOCTL_NR(DRM_IOCTL_DMA)) && dev->driver->dma_ioctl)
func = dev->driver->dma_ioctl;
if (!func) {
DRM_DEBUG(quot;no functionnquot;);
retcode = -EINVAL;
} else if (((ioctl->flags & DRM_ROOT_ONLY) && !capable(CAP_SYS_ADMIN)) ||
((ioctl->flags & DRM_AUTH) && !priv->authenticated) ||
((ioctl->flags & DRM_MASTER) && !priv->master)) {
retcode = -EACCES;
} else {
retcode = func(inode, filp, cmd, arg);
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

12. DRM Authentication
(linux/drivers/char/drm/drm_auth.c: Cookie Issuer)
int drm_getmagic(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
{
...
typedef unsigned int drm_magic_t;
/* Find unique magic */
if (priv->magic) {
typedef struct drm_auth {
auth.magic = priv->magic;
drm_magic_t magic;
} else {
do { } drm_auth_t;
spin_lock(&lock);
if (!sequence)
++sequence;/* reserve 0 */
auth.magic = sequence++;
spin_unlock(&lock);
} while (drm_find_file(dev, auth.magic));
priv->magic = auth.magic;
drm_add_magic(dev, priv, auth.magic);
}
DRM_DEBUG(quot;%unquot;, auth.magic);
if (copy_to_user((drm_auth_t __user *) arg, &auth, sizeof(auth)))
return -EFAULT;
return 0;
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

13. DRM Authentication
(linux/drivers/char/drm/drm_auth.c: Cookie Verifier)
int drm_authmagic(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
{
drm_file_t *priv = filp->private_data;
drm_device_t *dev = priv->head->dev;
drm_auth_t auth;
drm_file_t *file;
if (copy_from_user(&auth, (drm_auth_t __user *) arg, sizeof(auth)))
return -EFAULT;
DRM_DEBUG(quot;%unquot;, auth.magic);
if ((file = drm_find_file(dev, auth.magic))) {
file->authenticated = 1;
drm_remove_magic(dev, auth.magic);
return 0;
}
return -EINVAL;
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

14. DRM Authentication
(linux/drivers/char/drm/drm_auth.c: Cookie Keeper)
static drm_file_t *drm_find_file(drm_device_t * dev, drm_magic_t magic)
{
drm_file_t *retval = NULL;
drm_magic_entry_t *pt;
int hash = drm_hash_magic(magic);
mutex_lock(&dev->struct_mutex);
for (pt = dev->magiclist[hash].head; pt; pt = pt->next) {
if (pt->magic == magic) {
retval = pt->priv;
break;
}
}
mutex_unlock(&dev->struct_mutex);
return retval;
}
2007 © Moriyoshi Koizumi. All Rights Reserved.

15. Graphic Address Remapping Table
(GART)
SAREA
Frame Buffer Phy-Phy Address Translation
Texture Buffer Process #1
(by AGP controller)
Graphics
MMIO Aperture Virtual
Space Memory
Space
Physical
Process #2
Address
Space
Actual Virtual
RAM Memory
Space Space
GART
Phy-Virt Address
Translation (by MMU)
2007 © Moriyoshi Koizumi. All Rights Reserved.

16. AGPGART IOCTL I/F
ACQUIRE
●
SETUP
●
RESERVE
●
PROTECT
●
ALLOCATE / DEALLOCATE
●
BIND / UNBIND
●
2007 © Moriyoshi Koizumi. All Rights Reserved.