rtc-ds1307 exports NVRAM

Export the NVRAM on DS1307 and DS1338 chips, like several of the
other drivers do for such combination RTC-and-NVRAM chips.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 95 insertions, 2 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 7958635f12cc..e5cdc0294aaa 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -135,8 +135,8 @@ config RTC_DRV_DS1307
 
           The first seven registers on these chips hold an RTC, and other
           registers may add features such as NVRAM, a trickle charger for
-          the RTC/NVRAM backup power, and alarms.  This driver may not
-          expose all those available chip features.
+          the RTC/NVRAM backup power, and alarms.  NVRAM is visible in
+          sysfs, but other chip features may not be available.
 
           This driver can also be built as a module. If so, the module
           will be called rtc-ds1307.
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index db6f3f0d8982..bc1c7fe94ad3 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -89,6 +89,7 @@ enum ds_type {
 
 struct ds1307 {
         u8                      reg_addr;
+        bool                    has_nvram;
         u8                      regs[8];
         enum ds_type            type;
         struct i2c_msg          msg[2];
@@ -242,6 +243,87 @@ static const struct rtc_class_ops ds13xx_rtc_ops = {
         .set_time       = ds1307_set_time,
 };
 
+/*----------------------------------------------------------------------*/
+
+#define NVRAM_SIZE      56
+
+static ssize_t
+ds1307_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
+                char *buf, loff_t off, size_t count)
+{
+        struct i2c_client       *client;
+        struct ds1307           *ds1307;
+        struct i2c_msg          msg[2];
+        int                     result;
+
+        client = to_i2c_client(container_of(kobj, struct device, kobj));
+        ds1307 = i2c_get_clientdata(client);
+
+        if (unlikely(off >= NVRAM_SIZE))
+                return 0;
+        if ((off + count) > NVRAM_SIZE)
+                count = NVRAM_SIZE - off;
+        if (unlikely(!count))
+                return count;
+
+        msg[0].addr = client->addr;
+        msg[0].flags = 0;
+        msg[0].len = 1;
+        msg[0].buf = buf;
+
+        buf[0] = 8 + off;
+
+        msg[1].addr = client->addr;
+        msg[1].flags = I2C_M_RD;
+        msg[1].len = count;
+        msg[1].buf = buf;
+
+        result = i2c_transfer(to_i2c_adapter(client->dev.parent), msg, 2);
+        if (result != 2) {
+                dev_err(&client->dev, "%s error %d\n", "nvram read", result);
+                return -EIO;
+        }
+        return count;
+}
+
+static ssize_t
+ds1307_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
+                char *buf, loff_t off, size_t count)
+{
+        struct i2c_client       *client;
+        u8                      buffer[NVRAM_SIZE + 1];
+        int                     ret;
+
+        client = to_i2c_client(container_of(kobj, struct device, kobj));
+
+        if (unlikely(off >= NVRAM_SIZE))
+                return -EFBIG;
+        if ((off + count) > NVRAM_SIZE)
+                count = NVRAM_SIZE - off;
+        if (unlikely(!count))
+                return count;
+
+        buffer[0] = 8 + off;
+        memcpy(buffer + 1, buf, count);
+
+        ret = i2c_master_send(client, buffer, count + 1);
+        return (ret < 0) ? ret : (ret - 1);
+}
+
+static struct bin_attribute nvram = {
+        .attr = {
+                .name   = "nvram",
+                .mode   = S_IRUGO | S_IWUSR,
+                .owner  = THIS_MODULE,
+        },
+
+        .read   = ds1307_nvram_read,
+        .write  = ds1307_nvram_write,
+        .size   = NVRAM_SIZE,
+};
+
+/*----------------------------------------------------------------------*/
+
 static struct i2c_driver ds1307_driver;
 
 static int __devinit ds1307_probe(struct i2c_client *client)
@@ -413,6 +495,14 @@ read_rtc:
                 goto exit_free;
         }
 
+        if (chip->nvram56) {
+                err = sysfs_create_bin_file(&client->dev.kobj, &nvram);
+                if (err == 0) {
+                        ds1307->has_nvram = true;
+                        dev_info(&client->dev, "56 bytes nvram\n");
+                }
+        }
+
         return 0;
 
 exit_bad:
@@ -432,6 +522,9 @@ static int __devexit ds1307_remove(struct i2c_client *client)
 {
         struct ds1307   *ds1307 = i2c_get_clientdata(client);
 
+        if (ds1307->has_nvram)
+                sysfs_remove_bin_file(&client->dev.kobj, &nvram);
+
         rtc_device_unregister(ds1307->rtc);
         kfree(ds1307);
         return 0;