Precaution to access user mode buffers from kernel


 
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Old 07-17-2012
Precaution to access user mode buffers from kernel

When accessing a user mode buffers from kernel space drivers what precautions must we take and how those precautions need to be implemented?
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GLDRAWBUFFER(3G)						   OpenGL Manual						  GLDRAWBUFFER(3G)

NAME
glDrawBuffer - specify which color buffers are to be drawn into C SPECIFICATION
void glDrawBuffer(GLenum mode); PARAMETERS
mode Specifies up to four color buffers to be drawn into. Symbolic constants GL_NONE, GL_FRONT_LEFT, GL_FRONT_RIGHT, GL_BACK_LEFT, GL_BACK_RIGHT, GL_FRONT, GL_BACK, GL_LEFT, GL_RIGHT, and GL_FRONT_AND_BACK are accepted. The initial value is GL_FRONT for single-buffered contexts, and GL_BACK for double-buffered contexts. DESCRIPTION
When colors are written to the frame buffer, they are written into the color buffers specified by glDrawBuffer. The specifications are as follows: GL_NONE No color buffers are written. GL_FRONT_LEFT Only the front left color buffer is written. GL_FRONT_RIGHT Only the front right color buffer is written. GL_BACK_LEFT Only the back left color buffer is written. GL_BACK_RIGHT Only the back right color buffer is written. GL_FRONT Only the front left and front right color buffers are written. If there is no front right color buffer, only the front left color buffer is written. GL_BACK Only the back left and back right color buffers are written. If there is no back right color buffer, only the back left color buffer is written. GL_LEFT Only the front left and back left color buffers are written. If there is no back left color buffer, only the front left color buffer is written. GL_RIGHT Only the front right and back right color buffers are written. If there is no back right color buffer, only the front right color buffer is written. GL_FRONT_AND_BACK All the front and back color buffers (front left, front right, back left, back right) are written. If there are no back color buffers, only the front left and front right color buffers are written. If there are no right color buffers, only the front left and back left color buffers are written. If there are no right or back color buffers, only the front left color buffer is written. If more than one color buffer is selected for drawing, then blending or logical operations are computed and applied independently for each color buffer and can produce different results in each buffer. Monoscopic contexts include only left buffers, and stereoscopic contexts include both left and right buffers. Likewise, single-buffered contexts include only front buffers, and double-buffered contexts include both front and back buffers. The context is selected at GL initialization. ERRORS
GL_INVALID_ENUM is generated if mode is not an accepted value. GL_INVALID_OPERATION is generated if none of the buffers indicated by mode exists. ASSOCIATED GETS
glGet() with argument GL_DRAW_BUFFER SEE ALSO
glBlendFunc(), glColorMask(), glDrawBuffers(), glLogicOp(), glReadBuffer() COPYRIGHT
Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/. AUTHORS
opengl.org opengl.org 06/10/2014 GLDRAWBUFFER(3G)