[PATCH v2] rtc: ds1307: generalise ram size and offset

[Austin Boyle <Austin.Boyle@aviatnet.com>]

From: Austin Boyle <Austin.Boyle@aviatnet.com>

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

Cc: Wolfram Sang <w.sang@pengutronix.de>
Cc: David Anderson <danders.dev@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Austin Boyle <Austin.Boyle@aviatnet.com>
---
this patch is based on Wolfram Sang's tree:
git://git.pengutronix.de/git/wsa/linux-2.6.git ds1307

patch depends on:
rtc: ds1307: comment and format cleanup 21af5f7bd6
rtc: ds1307: simplify irq setup code  8c63e03627
rtc: ds1307: refactor chip_desc table e246db081d
rtc: add initial support for mcp7941x parts e69bba2d3a

--- a/drivers/rtc/rtc-ds1307.c	2011-10-10 11:22:22.674690998 +1300
+++ b/drivers/rtc/rtc-ds1307.c	2011-11-03 12:17:40.777642801 +1300
@@ -104,6 +104,8 @@ enum ds_type {
 
 struct ds1307 {
 	u8			offset; /* register's offset */
+	u16			nvram_offset;
+	u16			nvram_size;
 	u8			regs[11];
 	enum ds_type		type;
 	unsigned long		flags;
@@ -119,19 +121,19 @@ struct ds1307 {
 };
 
 struct chip_desc {
-	unsigned		nvram56:1;
+	unsigned		nvram:1;
 	unsigned		alarm:1;
 };
 
 static const struct chip_desc chips[last_ds_type] = {
 	[ds_1307] = {
-		.nvram56	= 1,
+		.nvram		= 1,
 	},
 	[ds_1337] = {
 		.alarm		= 1,
 	},
 	[ds_1338] = {
-		.nvram56	= 1,
+		.nvram		= 1,
 	},
 	[ds_1339] = {
 		.alarm		= 1,
@@ -139,6 +141,9 @@ static const struct chip_desc chips[last
 	[ds_3231] = {
 		.alarm		= 1,
 	},
+	[mcp7941x] = {
+		.nvram		= 1,
+	},
 };
 
 static const struct i2c_device_id ds1307_id[] = {
@@ -543,8 +548,6 @@ static const struct rtc_class_ops ds13xx
 
 /*----------------------------------------------------------------------*/
 
-#define NVRAM_SIZE	56
-
 static ssize_t
 ds1307_nvram_read(struct file *filp, struct kobject *kobj,
 		struct bin_attribute *attr,
@@ -557,14 +560,15 @@ ds1307_nvram_read(struct file *filp, str
 	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 +586,15 @@ ds1307_nvram_write(struct file *filp, st
 	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;
@@ -605,7 +610,6 @@ static struct bin_attribute nvram = {
 
 	.read	= ds1307_nvram_read,
 	.write	= ds1307_nvram_write,
-	.size	= NVRAM_SIZE,
 };
 
 /*----------------------------------------------------------------------*/
@@ -692,6 +696,9 @@ static int __devinit ds1307_probe(struct
 		break;
 
 	case rx_8025:
+		ds1307->nvram_size = 64; /* 64 bytes SRAM */
+		ds1307->nvram_offset = 0x20;
+
 		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
 				RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
 		if (tmp != 2) {
@@ -758,6 +765,8 @@ static int __devinit ds1307_probe(struct
 		break;
 	case ds_1388:
 		ds1307->offset = 1; /* Seconds starts at 1 */
+		ds1307->nvram_size = 56; /* 56 bytes NVRAM */
+		ds1307->nvram_offset = 8;
 		break;
 	default:
 		break;
@@ -893,11 +902,12 @@ read_rtc:
 		dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
 	}
 
-	if (chip && chip->nvram56) {
+	if (chip && chip->nvram) {
+		nvram.size = ds1307->nvram_size;
 		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");
+			dev_info(&client->dev, "%zd bytes nvram\n", nvram.size);
 		}
 	}