typing
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David Schleef
parent
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commit
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1 changed files with 160 additions and 25 deletions
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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
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<glossary>
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<title>
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Glossary
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</title>
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<glossentry>
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<glossterm>
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buffer
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</glossterm>
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<glossdef>
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<para>
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Comedi uses permanently allocated kernel memory for streaming input
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and output to store data that has been measured by a device, but has
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not been read by an application. These buffers can be resized by the
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Comedilib function comedi_buffer_XXX() or the coemdi_config
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utility.
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</para>
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</glossdef>
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</glossentry>
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Buffer:
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<glossentry>
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<glossterm>
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buffer overflow
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</glossterm>
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<glossdef>
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<para>
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This is an error message that indicates that the driver ran out of
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space in a Comedi buffer to put samples. It means that the application
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is not copying data out of the buffer quickly enough. Often, this
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problem can be fixed by making the Comedi buffer larger. See
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comedi_buffer_XXX for more information.
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>
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overrun
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</glossterm>
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<glossdef>
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<para>
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This is an error message that indicates that there was device-level
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problem, typically with trigger pulses occurring faster than the
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board can handle.
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</para>
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</glossdef>
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</glossentry>
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Buffer Overflow:
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Buffer Overrun:
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Command:
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<glossentry>
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<glossterm>
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command
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</glossterm>
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<glossdef>
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<para>
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Comedi commands are the mechanism that applications configure
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subdevices for streaming input and output.
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(also: cmd, comedi_command)
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>
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DMA
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</glossterm>
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<glossdef>
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<para>
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Direct memory access. DMA is a method of transferring data between
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a device and the main memory of a computer. DMA operates differently
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on ISA and PCI cards. ISA DMA is handled by a controller on the
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motherboard and is limited to transfers to/from the lowest 16 MB of
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physical RAM and can only handle a single segment of memory at a time.
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These limitations make it almost useless. PCI ("bus mastering") DMA
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is handled by a controller on the device, and can typically address
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4 GB of RAM and handle many segments of memory simultaneously. DMA
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is usually not the only means to data transfer, and may or may not
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be the optimal transfer mechanism for a particular situation.
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</para>
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</glossdef>
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</glossentry>
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DMA:
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<glossentry>
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<glossterm>
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FIFO
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</glossterm>
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<glossdef>
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<para>
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Most devices have a limited amount of on-board space to store samples
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before they are transferred to the Comedi buffer. This allows the CPU or
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DMA controller to do other things, and then efficiently process a
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large number of samples simultaneously. It also increases the
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maximum interrupt latency that the system can handle without
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interruptions in data.
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</para>
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</glossdef>
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</glossentry>
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FIFO:
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Instruction:
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<glossentry>
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<glossterm>
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instruction
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</glossterm>
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<glossdef>
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<para>
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Comedi instructions are the mechanism used by applications to do
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immediate input from channels, output to channels, and configuration
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of subdevices and channels.
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(also: insn)
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Instruction List:
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Configuration Options:
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(also: Options, Option List)
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Poll:
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>
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instruction list
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</glossterm>
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<glossdef>
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<para>
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Instruction lists allow the application to perform multiple Comedi
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instructions in the same system call.
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>
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option list
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</glossterm>
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<glossdef>
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<para>
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Option lists are used with comedi_config to perform driver
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configuration.
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(also: configuration options, options)
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</para>
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</glossdef>
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</glossentry>
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<glossentry>
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<glossterm>
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poll
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</glossterm>
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<glossdef>
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<para>
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The term poll (and polling) is used for several different related
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concepts in Comedi. Comedi implements the poll() system call for
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Comedi devices, which is similar to select(), and returns information
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about file descriptors that can be read or written. Comedilib also
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has a function called comedi_poll(), which causes the driver to
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copy all available data from the device to the Comedi buffer. In
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addition, some drivers may use a polling technique in place of
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interrupts.
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</para>
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</glossdef>
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</glossentry>
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<!--
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<glossentry>
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<glossterm>
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</glossterm>
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<glossdef>
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<para>
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</para>
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</glossdef>
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</glossentry>
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-->
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</glossary>
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