samples: Add random driver sample.

Change-Id: If0552cbd478e49c71bbfa02448113a3a0e3b4463
Signed-off-by: Marcus Shawcroft <marcus.shawcroft@arm.com>

samples/drivers/random/Makefile

@@ -0,0 +1,4 @@
+BOARD ?= frdm_k64f
+CONF_FILE = prj.conf
+
+include ${ZEPHYR_BASE}/Makefile.inc

samples/drivers/random/README.txt

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+Title: Random
+
+Description:
+
+A simple random number generation example
+
+--------------------------------------------------------------------------------
+
+Building and Running Project:
+
+This project writes an infinite series of random numbers to the
+console, 10 per second.
+
+It can be built and executed on frdm_k64f as follows:
+
+    make
+
+Sample Output:
+
+Random Example! arm
+random device is 0x2000008c, name is RANDOM_0
+  0xd7  0x42  0xb0  0x7b  0x56  0x3b  0xc3  0x43  0x8a  0xa3
+  0xfa  0xec  0xd8  0xc3  0x36  0xf8  0x7b  0x82  0x2b  0x39

samples/drivers/random/prj.conf

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+CONFIG_RANDOM_GENERATOR=y
+CONFIG_STDOUT_CONSOLE=y

samples/drivers/random/src/Makefile

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+obj-y = main.o

samples/drivers/random/src/main.c

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+/*
+ * Copyright (c) 2016 ARM Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <zephyr.h>
+#include <random.h>
+#include <stdio.h>
+
+void main(void)
+{
+	struct device *dev;
+
+	printf("Random Example! %s\n", CONFIG_ARCH);
+
+	dev = device_get_binding(CONFIG_RANDOM_NAME);
+	if (!dev) {
+		printf("error: no random device\n");
+		return;
+	}
+
+	printf("random device is %p, name is %s\n",
+	       dev, dev->config->name);
+
+	while (1) {
+#define BUFFER_LENGTH 10
+		uint8_t buffer[BUFFER_LENGTH];
+		int r;
+
+		r = random_get_entropy(dev, buffer, BUFFER_LENGTH);
+		if (r) {
+			printf("random_get_entropy failed: %d\n", r);
+			break;
+		};
+
+		for (int i = 0; i < BUFFER_LENGTH; i++) {
+			printf("  0x%x", buffer[i]);
+		};
+
+		printf("\n");
+
+		k_sleep(1000);
+	}
+}

samples/drivers/random/testcase.ini

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+[test]
+build_only = true
+tags = samples