DRM_IOCTL_VIA_DMA_INIT DRM_IOCTL_VIA_CMDBUFFER DRM_IOCTL_VIA_FLUSH
The first ioctl sets up an area in AGP memory that will be used as the ring
buffer. The second ioctl copies a command buffer from user space memory
to the ring buffer. The third ioctl waits for engine idle until it
returns.
The motivation for this patch is to avoid the wait for engine idle call
before each buffer flush in the current DRI driver. With this patch,
the DRI driver can continue to flush its buffer as long as there is
free space in the ring buffer.
This patch adds an additional copy operation on the command buffer. This
buffer copying is necessary to support multiple DRI clients rendering
simultaneously. Otherwise, more CPU time will be spent in the busy loop
waiting for engine idle between DRI context switch. Even in the single
client case, the tradeoff is reasonable in comparision to the kernel
call to check for free buffer space for the client to render directly
to the ring buffer.
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* For the very latest on DRI development, please see: *
* http://dri.sourceforge.net/ *
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The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://precisioninsight.com/piinsights.html
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://precisioninsight.com/dr/drm.html
Hardware Locking for the Direct Rendering Infrastructure
http://precisioninsight.com/dr/locking.html
A Security Analysis of the Direct Rendering Infrastructure
http://precisioninsight.com/dr/security.html
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.sourceforge.net/ *
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