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--- gpiomem [2017/02/03 10:34]
brian.kim created
+++ gpiomem [2017/02/03 10:44] (current)
brian.kim
@@ Line 21: / Line 21: @@
 SUBSYSTEM=="exynos-gpiomem", GROUP="gpio", MODE="0660"
 </code>
+==== Example ====
+Hardkernel's wiringPi library which is for GPIO control uses ///dev/gpiomem// device file for rootless gpio control. Usage is very simple. Just open ///dev/gpiomem// device file instead of ///dev/mem//.
+  * [[https://github.com/hardkernel/wiringPi/blob/master/wiringPi/wiringPi.c#L2868-L2879|($HK_WIRINGPI)/wiringPi/wiringPi.c]]
+<code>
+  // Open the master /dev/memory device
+  if (access("/dev/gpiomem",0) == 0) {
+    if ((fd = open ("/dev/gpiomem", O_RDWR | O_SYNC | O_CLOEXEC) ) < 0)
+      return wiringPiFailure (WPI_ALMOST, "wiringPiSetup: Unable to open /dev/gpiomem: %s\n", strerror (errno)) ;
+  }
+  else {
+    if (geteuid () != 0)
+      (void)wiringPiFailure (WPI_FATAL, "wiringPiSetup: Must be root. (Did you forget sudo?)\n") ;
+    if ((fd = open ("/dev/mem", O_RDWR | O_SYNC | O_CLOEXEC) ) < 0)
+      return wiringPiFailure (WPI_ALMOST, "wiringPiSetup: Unable to open /dev/mem: %s\n", strerror (errno)) ;
+  }
+</code>