From c3c76ef3d50f71a7bef2994df462c5add11658d9 Mon Sep 17 00:00:00 2001
From: Lorenz Meier <lm@inf.ethz.ch>
Date: Mon, 29 Oct 2012 09:44:59 +0100
Subject: Hardened the EEPROM attach routine for param storage

---
 apps/systemcmds/eeprom/24xxxx_mtd.c | 27 +++++++++++++++++++++++++++
 apps/systemcmds/eeprom/eeprom.c     | 14 ++++++++++++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/apps/systemcmds/eeprom/24xxxx_mtd.c b/apps/systemcmds/eeprom/24xxxx_mtd.c
index 79149caa0..781b01065 100644
--- a/apps/systemcmds/eeprom/24xxxx_mtd.c
+++ b/apps/systemcmds/eeprom/24xxxx_mtd.c
@@ -502,6 +502,33 @@ FAR struct mtd_dev_s *at24c_initialize(FAR struct i2c_dev_s *dev) {
 		priv->perf_write_errors = perf_alloc(PC_COUNT, "EEPROM write errors");
 	}
 
+	/* attempt to read to validate device is present */
+	unsigned char buf[5];
+	uint8_t addrbuf[2] = {0, 0};
+
+	struct i2c_msg_s msgv[2] = {
+		{
+			.addr = priv->addr,
+			.flags = 0,
+			.buffer = &addrbuf[0],
+			.length = sizeof(addrbuf),
+		},
+		{
+			.addr = priv->addr,
+			.flags = I2C_M_READ,
+			.buffer = &buf[0],
+			.length = sizeof(buf),
+		}
+	};
+
+	perf_begin(priv->perf_reads);
+	int ret = I2C_TRANSFER(priv->dev, &msgv[0], 2);
+	perf_end(priv->perf_reads);
+
+	if (ret < 0) {
+		return NULL;
+	}
+
 	/* Return the implementation-specific state structure as the MTD device */
 
 	fvdbg("Return %p\n", priv);
diff --git a/apps/systemcmds/eeprom/eeprom.c b/apps/systemcmds/eeprom/eeprom.c
index 19a14aa02..b4257cda9 100644
--- a/apps/systemcmds/eeprom/eeprom.c
+++ b/apps/systemcmds/eeprom/eeprom.c
@@ -118,9 +118,19 @@ eeprom_attach(void)
 	if (i2c == NULL)
 		errx(1, "failed to locate I2C bus");
 
-	/* start the MTD driver */
-	eeprom_mtd = at24c_initialize(i2c);
+	/* start the MTD driver, attempt 5 times */
+	for (int i = 0; i < 5; i++) {
+		eeprom_mtd = at24c_initialize(i2c);
+		if (eeprom_mtd) {
+			/* abort on first valid result */
+			if (i > 0) {
+				warnx("warning: EEPROM needed %d attempts to attach", i+1);
+			}
+			break;
+		}
+	}
 
+	/* if last attempt is still unsuccessful, abort */
 	if (eeprom_mtd == NULL)
 		errx(1, "failed to initialize EEPROM driver");
 
-- 
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