1 files changed, 56 insertions, 1 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index c837507dfb1c..575730744fdb 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -250,6 +250,43 @@ static ssize_t mtd_name_show(struct device *dev,
 }
 static DEVICE_ATTR(name, S_IRUGO, mtd_name_show, NULL);
 
+static ssize_t mtd_ecc_strength_show(struct device *dev,
+                                     struct device_attribute *attr, char *buf)
+{
+        struct mtd_info *mtd = dev_get_drvdata(dev);
+
+        return snprintf(buf, PAGE_SIZE, "%u\n", mtd->ecc_strength);
+}
+static DEVICE_ATTR(ecc_strength, S_IRUGO, mtd_ecc_strength_show, NULL);
+
+static ssize_t mtd_bitflip_threshold_show(struct device *dev,
+                                          struct device_attribute *attr,
+                                          char *buf)
+{
+        struct mtd_info *mtd = dev_get_drvdata(dev);
+
+        return snprintf(buf, PAGE_SIZE, "%u\n", mtd->bitflip_threshold);
+}
+
+static ssize_t mtd_bitflip_threshold_store(struct device *dev,
+                                           struct device_attribute *attr,
+                                           const char *buf, size_t count)
+{
+        struct mtd_info *mtd = dev_get_drvdata(dev);
+        unsigned int bitflip_threshold;
+        int retval;
+
+        retval = kstrtouint(buf, 0, &bitflip_threshold);
+        if (retval)
+                return retval;
+
+        mtd->bitflip_threshold = bitflip_threshold;
+        return count;
+}
+static DEVICE_ATTR(bitflip_threshold, S_IRUGO | S_IWUSR,
+                   mtd_bitflip_threshold_show,
+                   mtd_bitflip_threshold_store);
+
 static struct attribute *mtd_attrs[] = {
         &dev_attr_type.attr,
         &dev_attr_flags.attr,
@@ -260,6 +297,8 @@ static struct attribute *mtd_attrs[] = {
         &dev_attr_oobsize.attr,
         &dev_attr_numeraseregions.attr,
         &dev_attr_name.attr,
+        &dev_attr_ecc_strength.attr,
+        &dev_attr_bitflip_threshold.attr,
         NULL,
 };
 
@@ -322,6 +361,10 @@ int add_mtd_device(struct mtd_info *mtd)
         mtd->index = i;
         mtd->usecount = 0;
 
+        /* default value if not set by driver */
+        if (mtd->bitflip_threshold == 0)
+                mtd->bitflip_threshold = mtd->ecc_strength;
+
         if (is_power_of_2(mtd->erasesize))
                 mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
         else
@@ -757,12 +800,24 @@ EXPORT_SYMBOL_GPL(mtd_get_unmapped_area);
 int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
              u_char *buf)
 {
+        int ret_code;
         *retlen = 0;
         if (from < 0 || from > mtd->size || len > mtd->size - from)
                 return -EINVAL;
         if (!len)
                 return 0;
-        return mtd->_read(mtd, from, len, retlen, buf);
+
+        /*
+         * In the absence of an error, drivers return a non-negative integer
+         * representing the maximum number of bitflips that were corrected on
+         * any one ecc region (if applicable; zero otherwise).
+         */
+        ret_code = mtd->_read(mtd, from, len, retlen, buf);
+        if (unlikely(ret_code < 0))
+                return ret_code;
+        if (mtd->ecc_strength == 0)
+                return 0;       /* device lacks ecc */
+        return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
 }
 EXPORT_SYMBOL_GPL(mtd_read);