📄 device_files.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html><head> <title></title> <link rel="stylesheet" media="screen" type="text/css" href="./style.css" /> <link rel="stylesheet" media="screen" type="text/css" href="./design.css" /> <link rel="stylesheet" media="print" type="text/css" href="./print.css" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body><a href=start.html>start</a></br><h2><a name="device_files" id="device_files">Device Files</a></h2><div class="level2"><p>Device files are stored in the directory <code>/dev</code>. The files stored in this directory represent both physical (actual hardware) and logical devices (devices which implement special system functions e.g. <code>/dev/null</code>). In Linux devices are mapped to device files to provide congruity. For example, this mapping allows function calls such as open, close, read, write, etc. to be functional for devices as well as files. uClinux for Blackfin provides several device files which are mapped to both on and off chip hardware. A description of some of the device files is given below: </p><ul><li class="level1"><div class="li"><code><strong>/dev/console</strong></code> - This device file is mapped to the console.</div></li><li class="level1"><div class="li"><code><strong>/dev/dsp</strong></code> - This device is mapped to any audio codecs that are available.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>kmem</strong></code> - This device is mapped to kernel memory space.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>mem</strong></code> - {Unsure how exactly this is mapped in the context of Blackfin}</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>mtd</strong></code><code><strong>#</strong></code> - This device provides raw character access to the flash memory.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>mtdblock</strong></code><code><strong>#</strong></code> - This device provides block access to the flash memory.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>mtdr</strong></code><code><strong>#</strong></code> - This device provides read-only raw character access to the flash memory.</div></li><li class="level1"><div class="li"><code><strong>/dev/null</strong></code> - Everything written to this device is discarded. Reading from this device returns nothing.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>pflbutton</strong></code> - {To be added}</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>pflag</strong></code><code><strong>#</strong></code> - This device file is mapped to a programmable flag on the Blackfin device.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>ptyp</strong></code><code><strong>#</strong></code> - {To be added}</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>ppp</strong></code> - {To be added}</div></li><li class="level1"><div class="li"><code><strong>/dev/ram0</strong></code> - This device file is mapped to {unsure if this is on or off chip ram}. It is used as part of the simple RAM based file system.</div></li><li class="level1"><div class="li"><code><strong>/dev/ram1</strong></code> - This device file is mapped to {unsure which RAM section this is mapped to}.</div></li><li class="level1"><div class="li"><code><strong>/dev/random</strong></code> - This device file generates random numbers. Depending on the particular situation it may be slower than /dev/urandom but its output tends to be harder to predict (i.e. closer to true randomness).</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>rtc</strong></code> - This device file is mapped to the Blackfin’s Real Time Clock (RTC).</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>spi</strong></code><code><strong>#</strong></code> - This device file is mapped to a Serial Peripheral Interface (SPI) on the Blackfin device.</div></li><li class="level1"><div class="li"><code><strong>/dev/sport#</strong></code> - This device file is mapped to a Serial Port (SPORT) on the Blackfin device.</div></li><li class="level1"><div class="li"><code><strong>/dev/time#</strong></code> - This device file is mapped to a timer on the Blackfin device.</div></li><li class="level1"><div class="li"><code><strong>/dev/tty</strong></code> - This device file is mapped to the current console.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>ttyS</strong></code><code><strong>#</strong></code> - This device file is mapped to a Universal Asynchronous Receiver Transmitter (UART) on the Blackfin device.</div></li><li class="level1"><div class="li"><code><strong>/dev/</strong></code><code><strong>ttyp</strong></code><code><strong>#</strong></code> - {To be added}</div></li><li class="level1"><div class="li"><code><strong>/dev/urandom</strong></code> - This device file generates random numbers. Depending on the particular situation it may be faster than /dev/random but in certain situation its output may be predictable (i.e. not truly random)</div></li><li class="level1"><div class="li"><code><strong>dev/zero</strong></code> - This device generates as many zeros as requested when it is read. This device cannot be written to.</div></li></ul></div></body></html>⌨️ 快捷键说明
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