rtc: ds1307: generalise ram size and offset

Generalise NVRAM to support RAM with other size and offset, such as the
64 bytes of SRAM on the mcp7941x.

[rdunlap@xenotime.net: fix printk format warning]
Signed-off-by: Austin Boyle <Austin.Boyle@aviatnet.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: David Anders <danders.dev@gmail.com>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 47 insertions, 31 deletions

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 84ab971978cf..cd188ab72f79 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -105,6 +105,8 @@ enum ds_type {
 struct ds1307 {
         u8                      offset; /* register's offset */
         u8                      regs[11];
+        u16                     nvram_offset;
+        struct bin_attribute    *nvram;
         enum ds_type            type;
         unsigned long           flags;
 #define HAS_NVRAM       0               /* bit 0 == sysfs file active */
@@ -119,19 +121,22 @@ struct ds1307 {
 };
 
 struct chip_desc {
-        unsigned                nvram56:1;
         unsigned                alarm:1;
+        u16                     nvram_offset;
+        u16                     nvram_size;
 };
 
 static const struct chip_desc chips[last_ds_type] = {
         [ds_1307] = {
-                .nvram56        = 1,
+                .nvram_offset   = 8,
+                .nvram_size     = 56,
         },
         [ds_1337] = {
                 .alarm          = 1,
         },
         [ds_1338] = {
-                .nvram56        = 1,
+                .nvram_offset   = 8,
+                .nvram_size     = 56,
         },
         [ds_1339] = {
                 .alarm          = 1,
@@ -139,6 +144,11 @@ static const struct chip_desc chips[last_ds_type] = {
         [ds_3231] = {
                 .alarm          = 1,
         },
+        [mcp7941x] = {
+                /* this is battery backed SRAM */
+                .nvram_offset   = 0x20,
+                .nvram_size     = 0x40,
+        },
 };
 
 static const struct i2c_device_id ds1307_id[] = {
@@ -543,8 +553,6 @@ static const struct rtc_class_ops ds13xx_rtc_ops = {
 
 /*----------------------------------------------------------------------*/
 
-#define NVRAM_SIZE      56
-
 static ssize_t
 ds1307_nvram_read(struct file *filp, struct kobject *kobj,
                 struct bin_attribute *attr,
@@ -557,14 +565,15 @@ ds1307_nvram_read(struct file *filp, struct kobject *kobj,
         client = kobj_to_i2c_client(kobj);
         ds1307 = i2c_get_clientdata(client);
 
-        if (unlikely(off >= NVRAM_SIZE))
+        if (unlikely(off >= ds1307->nvram->size))
                 return 0;
-        if ((off + count) > NVRAM_SIZE)
-                count = NVRAM_SIZE - off;
+        if ((off + count) > ds1307->nvram->size)
+                count = ds1307->nvram->size - off;
         if (unlikely(!count))
                 return count;
 
-        result = ds1307->read_block_data(client, 8 + off, count, buf);
+        result = ds1307->read_block_data(client, ds1307->nvram_offset + off,
+                                                                count, buf);
         if (result < 0)
                 dev_err(&client->dev, "%s error %d\n", "nvram read", result);
         return result;
@@ -582,14 +591,15 @@ ds1307_nvram_write(struct file *filp, struct kobject *kobj,
         client = kobj_to_i2c_client(kobj);
         ds1307 = i2c_get_clientdata(client);
 
-        if (unlikely(off >= NVRAM_SIZE))
+        if (unlikely(off >= ds1307->nvram->size))
                 return -EFBIG;
-        if ((off + count) > NVRAM_SIZE)
-                count = NVRAM_SIZE - off;
+        if ((off + count) > ds1307->nvram->size)
+                count = ds1307->nvram->size - off;
         if (unlikely(!count))
                 return count;
 
-        result = ds1307->write_block_data(client, 8 + off, count, buf);
+        result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
+                                                                count, buf);
         if (result < 0) {
                 dev_err(&client->dev, "%s error %d\n", "nvram write", result);
                 return result;
@@ -597,17 +607,6 @@ ds1307_nvram_write(struct file *filp, struct kobject *kobj,
         return count;
 }
 
-static struct bin_attribute nvram = {
-        .attr = {
-                .name   = "nvram",
-                .mode   = S_IRUGO | S_IWUSR,
-        },
-
-        .read   = ds1307_nvram_read,
-        .write  = ds1307_nvram_write,
-        .size   = NVRAM_SIZE,
-};
-
 /*----------------------------------------------------------------------*/
 
 static int __devinit ds1307_probe(struct i2c_client *client,
@@ -894,16 +893,31 @@ read_rtc:
                 dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
         }
 
-        if (chip->nvram56) {
-                err = sysfs_create_bin_file(&client->dev.kobj, &nvram);
-                if (err == 0) {
-                        set_bit(HAS_NVRAM, &ds1307->flags);
-                        dev_info(&client->dev, "56 bytes nvram\n");
+        if (chip->nvram_size) {
+                ds1307->nvram = kzalloc(sizeof(struct bin_attribute),
+                                                        GFP_KERNEL);
+                if (!ds1307->nvram) {
+                        err = -ENOMEM;
+                        goto exit_nvram;
+                }
+                ds1307->nvram->attr.name = "nvram";
+                ds1307->nvram->attr.mode = S_IRUGO | S_IWUSR;
+                ds1307->nvram->read = ds1307_nvram_read,
+                ds1307->nvram->write = ds1307_nvram_write,
+                ds1307->nvram->size = chip->nvram_size;
+                ds1307->nvram_offset = chip->nvram_offset;
+                err = sysfs_create_bin_file(&client->dev.kobj, ds1307->nvram);
+                if (err) {
+                        kfree(ds1307->nvram);
+                        goto exit_nvram;
                 }
+                set_bit(HAS_NVRAM, &ds1307->flags);
+                dev_info(&client->dev, "%zu bytes nvram\n", ds1307->nvram->size);
         }
 
         return 0;
 
+exit_nvram:
 exit_irq:
         rtc_device_unregister(ds1307->rtc);
 exit_free:
@@ -920,8 +934,10 @@ static int __devexit ds1307_remove(struct i2c_client *client)
                 cancel_work_sync(&ds1307->work);
         }
 
-        if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))
-                sysfs_remove_bin_file(&client->dev.kobj, &nvram);
+        if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags)) {
+                sysfs_remove_bin_file(&client->dev.kobj, ds1307->nvram);
+                kfree(ds1307->nvram);
+        }
 
         rtc_device_unregister(ds1307->rtc);
         kfree(ds1307);