From: David Schleef Date: Mon, 18 Mar 2002 23:12:58 +0000 (+0000) Subject: typing X-Git-Tag: r0_7_19~67 X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=80281d3b3138b193d7b07b4c365767eb71c34a84;p=comedilib.git typing --- diff --git a/doc/glossary.sgml b/doc/glossary.sgml index aaa74d6..23fd8ba 100644 --- a/doc/glossary.sgml +++ b/doc/glossary.sgml @@ -1,36 +1,171 @@ - - -Buffer: - - -Buffer Overflow: - - -Buffer Overrun: - - -Command: + + + + + Glossary + + + +buffer + + + +Comedi uses permanently allocated kernel memory for streaming input +and output to store data that has been measured by a device, but has +not been read by an application. These buffers can be resized by the +Comedilib function comedi_buffer_XXX() or the coemdi_config +utility. + + + + + + +buffer overflow + + + +This is an error message that indicates that the driver ran out of +space in a Comedi buffer to put samples. It means that the application +is not copying data out of the buffer quickly enough. Often, this +problem can be fixed by making the Comedi buffer larger. See +comedi_buffer_XXX for more information. + + + + + + +overrun + + + +This is an error message that indicates that there was device-level +problem, typically with trigger pulses occurring faster than the +board can handle. + + + + + + +command + + + +Comedi commands are the mechanism that applications configure +subdevices for streaming input and output. (also: cmd, comedi_command) - - -DMA: - - -FIFO: - - -Instruction: + + + + + + +DMA + + + +Direct memory access. DMA is a method of transferring data between +a device and the main memory of a computer. DMA operates differently +on ISA and PCI cards. ISA DMA is handled by a controller on the +motherboard and is limited to transfers to/from the lowest 16 MB of +physical RAM and can only handle a single segment of memory at a time. +These limitations make it almost useless. PCI ("bus mastering") DMA +is handled by a controller on the device, and can typically address +4 GB of RAM and handle many segments of memory simultaneously. DMA +is usually not the only means to data transfer, and may or may not +be the optimal transfer mechanism for a particular situation. + + + + + + +FIFO + + + +Most devices have a limited amount of on-board space to store samples +before they are transferred to the Comedi buffer. This allows the CPU or +DMA controller to do other things, and then efficiently process a +large number of samples simultaneously. It also increases the +maximum interrupt latency that the system can handle without +interruptions in data. + + + + + + +instruction + + + +Comedi instructions are the mechanism used by applications to do +immediate input from channels, output to channels, and configuration +of subdevices and channels. (also: insn) - - -Instruction List: - - -Configuration Options: - (also: Options, Option List) - - -Poll: - + + + + + + +instruction list + + + +Instruction lists allow the application to perform multiple Comedi +instructions in the same system call. + + + + + + +option list + + + +Option lists are used with comedi_config to perform driver +configuration. + (also: configuration options, options) + + + + + + +poll + + + +The term poll (and polling) is used for several different related +concepts in Comedi. Comedi implements the poll() system call for +Comedi devices, which is similar to select(), and returns information +about file descriptors that can be read or written. Comedilib also +has a function called comedi_poll(), which causes the driver to +copy all available data from the device to the Comedi buffer. In +addition, some drivers may use a polling technique in place of +interrupts. + + + + + + +