[PATCH] Update the rtc-rs5c372 driver

Bugfixes:
- Handle RTCs which are configured to use 12-hour mode.
- Never report bogus/un-initialized times.
- Displaying "raw trim" requires not masking it first!
- Fix the sysfs and procfs display of crystal and trim data.

Features:
- Handle other RTCs in this family, notably rv5c386/rv5c387.
- Declare the other registers.
- Provide alarm get/set functionality.
- Handle AIE and UIE; but no IRQ handling yet.

Cleanup:
- Shrink object by not including needless sysfs or procfs support
- We don't need no steenkin' forward declarations. (Except one.)

Until the I2C framework merges "new style" driver support, matching
the driver model better, using rv5c chips or alarm IRQs requires a
separate board-specific patch. (And an IRQ handler, handing off labor
through a work_struct...)

This uses the "method 3" register reads, but notes that it's done
to work around an evident i2c adapter driver bug.

Signed-off-by: David Brownell <[e-mail]>
Acked-by: Alessandro Zummo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-rs5c372.c

···
 /*
- * An I2C driver for the Ricoh RS5C372 RTC
+ * An I2C driver for Ricoh RS5C372 and RV5C38[67] RTCs
  *
  * Copyright (C) 2005 Pavel Mironchik <[e-mail]>
  * Copyright (C) 2006 Tower Technologies
···
 #include <linux/rtc.h>
 #include <linux/bcd.h>
 
-#define DRV_VERSION "0.3"
+#define DRV_VERSION "0.4"
 
 /* Addresses to scan */
 static unsigned short normal_i2c[] = { /* 0x32,*/ I2C_CLIENT_END };
···
 /* Insmod parameters */
 I2C_CLIENT_INSMOD;
 
+
+/*
+ * Ricoh has a family of I2C based RTCs, which differ only slightly from
+ * each other.  Differences center on pinout (e.g. how many interrupts,
+ * output clock, etc) and how the control registers are used.  The '372
+ * is significant only because that's the one this driver first supported.
+ */
 #define RS5C372_REG_SECS	0
 #define RS5C372_REG_MINS	1
 #define RS5C372_REG_HOURS	2
···
 #define RS5C372_REG_MONTH	5
 #define RS5C372_REG_YEAR	6
 #define RS5C372_REG_TRIM	7
+#	define RS5C372_TRIM_XSL		0x80
+#	define RS5C372_TRIM_MASK	0x7F
 
-#define RS5C372_TRIM_XSL	0x80
-#define RS5C372_TRIM_MASK	0x7F
+#define RS5C_REG_ALARM_A_MIN	8			/* or ALARM_W */
+#define RS5C_REG_ALARM_A_HOURS	9
+#define RS5C_REG_ALARM_A_WDAY	10
 
-#define RS5C372_REG_BASE	0
+#define RS5C_REG_ALARM_B_MIN	11			/* or ALARM_D */
+#define RS5C_REG_ALARM_B_HOURS	12
+#define RS5C_REG_ALARM_B_WDAY	13			/* (ALARM_B only) */
 
-static int rs5c372_attach(struct i2c_adapter *adapter);
-static int rs5c372_detach(struct i2c_client *client);
-static int rs5c372_probe(struct i2c_adapter *adapter, int address, int kind);
+#define RS5C_REG_CTRL1		14
+#	define RS5C_CTRL1_AALE		(1 << 7)	/* or WALE */
+#	define RS5C_CTRL1_BALE		(1 << 6)	/* or DALE */
+#	define RV5C387_CTRL1_24		(1 << 5)
+#	define RS5C372A_CTRL1_SL1	(1 << 5)
+#	define RS5C_CTRL1_CT_MASK	(7 << 0)
+#	define RS5C_CTRL1_CT0		(0 << 0)	/* no periodic irq */
+#	define RS5C_CTRL1_CT4		(4 << 0)	/* 1 Hz level irq */
+#define RS5C_REG_CTRL2		15
+#	define RS5C372_CTRL2_24		(1 << 5)
+#	define RS5C_CTRL2_XSTP		(1 << 4)
+#	define RS5C_CTRL2_CTFG		(1 << 2)
+#	define RS5C_CTRL2_AAFG		(1 << 1)	/* or WAFG */
+#	define RS5C_CTRL2_BAFG		(1 << 0)	/* or DAFG */
 
+
+/* to read (style 1) or write registers starting at R */
+#define RS5C_ADDR(R)		(((R) << 4) | 0)
+
+
+enum rtc_type {
+	rtc_undef = 0,
+	rtc_rs5c372a,
+	rtc_rs5c372b,
+	rtc_rv5c386,
+	rtc_rv5c387a,
+};
+
+/* REVISIT:  this assumes that:
+ *  - we're in the 21st century, so it's safe to ignore the century
+ *    bit for rv5c38[67] (REG_MONTH bit 7);
+ *  - we should use ALARM_A not ALARM_B (may be wrong on some boards)
+ */
 struct rs5c372 {
-	u8 reg_addr;
-	u8 regs[17];
-	struct i2c_msg msg[1];
-	struct i2c_client client;
-	struct rtc_device *rtc;
+	struct i2c_client	*client;
+	struct rtc_device	*rtc;
+	enum rtc_type		type;
+	unsigned		time24:1;
+	unsigned		has_irq:1;
+	char			buf[17];
+	char			*regs;
+
+	/* on conversion to a "new style" i2c driver, this vanishes */
+	struct i2c_client	dev;
 };
 
-static struct i2c_driver rs5c372_driver = {
-	.driver		= {
-		.name	= "rs5c372",
-	},
-	.attach_adapter	= &rs5c372_attach,
-	.detach_client	= &rs5c372_detach,
-};
-
-static int rs5c372_get_datetime(struct i2c_client *client, struct rtc_time *tm)
+static int rs5c_get_regs(struct rs5c372 *rs5c)
 {
+	struct i2c_client	*client = rs5c->client;
+	struct i2c_msg		msgs[] = {
+		{ client->addr, I2C_M_RD, sizeof rs5c->buf, rs5c->buf },
+	};
 
-	struct rs5c372 *rs5c372 = i2c_get_clientdata(client);
-	u8 *buf = &(rs5c372->regs[1]);
-
-	/* this implements the 3rd reading method, according
-	 * to the datasheet. rs5c372 defaults to internal
-	 * address 0xF, so 0x0 is in regs[1]
+	/* This implements the third reading method from the datasheet, using
+	 * an internal address that's reset after each transaction (by STOP)
+	 * to 0x0f ... so we read extra registers, and skip the first one.
+	 *
+	 * The first method doesn't work with the iop3xx adapter driver, on at
+	 * least 80219 chips; this works around that bug.
 	 */
-
-	if ((i2c_transfer(client->adapter, rs5c372->msg, 1)) != 1) {
-		dev_err(&client->dev, "%s: read error\n", __FUNCTION__);
+	if ((i2c_transfer(client->adapter, msgs, 1)) != 1) {
+		pr_debug("%s: can't read registers\n", rs5c->rtc->name);
 		return -EIO;
 	}
 
-	tm->tm_sec = BCD2BIN(buf[RS5C372_REG_SECS] & 0x7f);
-	tm->tm_min = BCD2BIN(buf[RS5C372_REG_MINS] & 0x7f);
-	tm->tm_hour = BCD2BIN(buf[RS5C372_REG_HOURS] & 0x3f);
-	tm->tm_wday = BCD2BIN(buf[RS5C372_REG_WDAY] & 0x07);
-	tm->tm_mday = BCD2BIN(buf[RS5C372_REG_DAY] & 0x3f);
+	dev_dbg(&client->dev,
+		"%02x %02x %02x (%02x) %02x %02x %02x (%02x), "
+		"%02x %02x %02x, %02x %02x %02x; %02x %02x\n",
+		rs5c->regs[0],  rs5c->regs[1],  rs5c->regs[2],  rs5c->regs[3],
+		rs5c->regs[4],  rs5c->regs[5],  rs5c->regs[6],  rs5c->regs[7],
+		rs5c->regs[8],  rs5c->regs[9],  rs5c->regs[10], rs5c->regs[11],
+		rs5c->regs[12], rs5c->regs[13], rs5c->regs[14], rs5c->regs[15]);
+
+	return 0;
+}
+
+static unsigned rs5c_reg2hr(struct rs5c372 *rs5c, unsigned reg)
+{
+	unsigned	hour;
+
+	if (rs5c->time24)
+		return BCD2BIN(reg & 0x3f);
+
+	hour = BCD2BIN(reg & 0x1f);
+	if (hour == 12)
+		hour = 0;
+	if (reg & 0x20)
+		hour += 12;
+	return hour;
+}
+
+static unsigned rs5c_hr2reg(struct rs5c372 *rs5c, unsigned hour)
+{
+	if (rs5c->time24)
+		return BIN2BCD(hour);
+
+	if (hour > 12)
+		return 0x20 | BIN2BCD(hour - 12);
+	if (hour == 12)
+		return 0x20 | BIN2BCD(12);
+	if (hour == 0)
+		return BIN2BCD(12);
+	return BIN2BCD(hour);
+}
+
+static int rs5c372_get_datetime(struct i2c_client *client, struct rtc_time *tm)
+{
+	struct rs5c372	*rs5c = i2c_get_clientdata(client);
+	int		status = rs5c_get_regs(rs5c);
+
+	if (status < 0)
+		return status;
+
+	tm->tm_sec = BCD2BIN(rs5c->regs[RS5C372_REG_SECS] & 0x7f);
+	tm->tm_min = BCD2BIN(rs5c->regs[RS5C372_REG_MINS] & 0x7f);
+	tm->tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C372_REG_HOURS]);
+
+	tm->tm_wday = BCD2BIN(rs5c->regs[RS5C372_REG_WDAY] & 0x07);
+	tm->tm_mday = BCD2BIN(rs5c->regs[RS5C372_REG_DAY] & 0x3f);
 
 	/* tm->tm_mon is zero-based */
-	tm->tm_mon = BCD2BIN(buf[RS5C372_REG_MONTH] & 0x1f) - 1;
+	tm->tm_mon = BCD2BIN(rs5c->regs[RS5C372_REG_MONTH] & 0x1f) - 1;
 
 	/* year is 1900 + tm->tm_year */
-	tm->tm_year = BCD2BIN(buf[RS5C372_REG_YEAR]) + 100;
+	tm->tm_year = BCD2BIN(rs5c->regs[RS5C372_REG_YEAR]) + 100;
 
 	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
 		"mday=%d, mon=%d, year=%d, wday=%d\n",
···
 		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
 
-	return 0;
+	/* rtc might need initialization */
+	return rtc_valid_tm(tm);
 }
 
 static int rs5c372_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
-	unsigned char buf[8] = { RS5C372_REG_BASE };
+	struct rs5c372	*rs5c = i2c_get_clientdata(client);
+	unsigned char	buf[8];
 
-	dev_dbg(&client->dev,
-		"%s: secs=%d, mins=%d, hours=%d "
+	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d "
 		"mday=%d, mon=%d, year=%d, wday=%d\n",
-		__FUNCTION__, tm->tm_sec, tm->tm_min, tm->tm_hour,
+		__FUNCTION__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
 
+	buf[0] = RS5C_ADDR(RS5C372_REG_SECS);
 	buf[1] = BIN2BCD(tm->tm_sec);
 	buf[2] = BIN2BCD(tm->tm_min);
-	buf[3] = BIN2BCD(tm->tm_hour);
+	buf[3] = rs5c_hr2reg(rs5c, tm->tm_hour);
 	buf[4] = BIN2BCD(tm->tm_wday);
 	buf[5] = BIN2BCD(tm->tm_mday);
 	buf[6] = BIN2BCD(tm->tm_mon + 1);
···
 	return 0;
 }
 
+#if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
+#define	NEED_TRIM
+#endif
+
+#if defined(CONFIG_RTC_INTF_SYSFS) || defined(CONFIG_RTC_INTF_SYSFS_MODULE)
+#define	NEED_TRIM
+#endif
+
+#ifdef	NEED_TRIM
 static int rs5c372_get_trim(struct i2c_client *client, int *osc, int *trim)
 {
 	struct rs5c372 *rs5c372 = i2c_get_clientdata(client);
-	u8 tmp = rs5c372->regs[RS5C372_REG_TRIM + 1];
+	u8 tmp = rs5c372->regs[RS5C372_REG_TRIM];
 
 	if (osc)
 		*osc = (tmp & RS5C372_TRIM_XSL) ? 32000 : 32768;
 
 	if (trim) {
-		*trim = tmp & RS5C372_TRIM_MASK;
-		dev_dbg(&client->dev, "%s: raw trim=%x\n", __FUNCTION__, *trim);
+		dev_dbg(&client->dev, "%s: raw trim=%x\n", __FUNCTION__, tmp);
+		tmp &= RS5C372_TRIM_MASK;
+		if (tmp & 0x3e) {
+			int t = tmp & 0x3f;
+
+			if (tmp & 0x40)
+				t = (~t | (s8)0xc0) + 1;
+			else
+				t = t - 1;
+
+			tmp = t * 2;
+		} else
+			tmp = 0;
+		*trim = tmp;
 	}
 
 	return 0;
 }
+#endif
 
 static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
···
 	return rs5c372_set_datetime(to_i2c_client(dev), tm);
 }
 
+#if defined(CONFIG_RTC_INTF_DEV) || defined(CONFIG_RTC_INTF_DEV_MODULE)
+
+static int
+rs5c_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	unsigned char		buf[2];
+	int			status;
+
+	buf[1] = rs5c->regs[RS5C_REG_CTRL1];
+	switch (cmd) {
+	case RTC_UIE_OFF:
+	case RTC_UIE_ON:
+		/* some 327a modes use a different IRQ pin for 1Hz irqs */
+		if (rs5c->type == rtc_rs5c372a
+				&& (buf[1] & RS5C372A_CTRL1_SL1))
+			return -ENOIOCTLCMD;
+	case RTC_AIE_OFF:
+	case RTC_AIE_ON:
+		/* these irq management calls only make sense for chips
+		 * which are wired up to an IRQ.
+		 */
+		if (!rs5c->has_irq)
+			return -ENOIOCTLCMD;
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+
+	buf[0] = RS5C_ADDR(RS5C_REG_CTRL1);
+	switch (cmd) {
+	case RTC_AIE_OFF:	/* alarm off */
+		buf[1] &= ~RS5C_CTRL1_AALE;
+		break;
+	case RTC_AIE_ON:	/* alarm on */
+		buf[1] |= RS5C_CTRL1_AALE;
+		break;
+	case RTC_UIE_OFF:	/* update off */
+		buf[1] &= ~RS5C_CTRL1_CT_MASK;
+		break;
+	case RTC_UIE_ON:	/* update on */
+		buf[1] &= ~RS5C_CTRL1_CT_MASK;
+		buf[1] |= RS5C_CTRL1_CT4;
+		break;
+	}
+	if ((i2c_master_send(client, buf, 2)) != 2) {
+		printk(KERN_WARNING "%s: can't update alarm\n",
+			rs5c->rtc->name);
+		status = -EIO;
+	} else
+		rs5c->regs[RS5C_REG_CTRL1] = buf[1];
+	return status;
+}
+
+#else
+#define	rs5c_rtc_ioctl	NULL
+#endif
+
+
+/* NOTE:  Since RTC_WKALM_{RD,SET} were originally defined for EFI,
+ * which only exposes a polled programming interface; and since
+ * these calls map directly to those EFI requests; we don't demand
+ * we have an IRQ for this chip when we go through this API.
+ *
+ * The older x86_pc derived RTC_ALM_{READ,SET} calls require irqs
+ * though, managed through RTC_AIE_{ON,OFF} requests.
+ */
+
+static int rs5c_read_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	int			status;
+
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+
+	/* report alarm time */
+	t->time.tm_sec = 0;
+	t->time.tm_min = BCD2BIN(rs5c->regs[RS5C_REG_ALARM_A_MIN] & 0x7f);
+	t->time.tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C_REG_ALARM_A_HOURS]);
+	t->time.tm_mday = -1;
+	t->time.tm_mon = -1;
+	t->time.tm_year = -1;
+	t->time.tm_wday = -1;
+	t->time.tm_yday = -1;
+	t->time.tm_isdst = -1;
+
+	/* ... and status */
+	t->enabled = !!(rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE);
+	t->pending = !!(rs5c->regs[RS5C_REG_CTRL2] & RS5C_CTRL2_AAFG);
+
+	return 0;
+}
+
+static int rs5c_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct i2c_client	*client = to_i2c_client(dev);
+	struct rs5c372		*rs5c = i2c_get_clientdata(client);
+	int			status;
+	unsigned char		buf[4];
+
+	/* only handle up to 24 hours in the future, like RTC_ALM_SET */
+	if (t->time.tm_mday != -1
+			|| t->time.tm_mon != -1
+			|| t->time.tm_year != -1)
+		return -EINVAL;
+
+	/* REVISIT: round up tm_sec */
+
+	/* if needed, disable irq (clears pending status) */
+	status = rs5c_get_regs(rs5c);
+	if (status < 0)
+		return status;
+	if (rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE) {
+		buf[0] = RS5C_ADDR(RS5C_REG_CTRL1);
+		buf[1] = rs5c->regs[RS5C_REG_CTRL1] & ~RS5C_CTRL1_AALE;
+		if (i2c_master_send(client, buf, 2) != 2) {
+			pr_debug("%s: can't disable alarm\n", rs5c->rtc->name);
+			return -EIO;
+		}
+		rs5c->regs[RS5C_REG_CTRL1] = buf[1];
+	}
+
+	/* set alarm */
+	buf[0] = RS5C_ADDR(RS5C_REG_ALARM_A_MIN);
+	buf[1] = BIN2BCD(t->time.tm_min);
+	buf[2] = rs5c_hr2reg(rs5c, t->time.tm_hour);
+	buf[3] = 0x7f;	/* any/all days */
+	if ((i2c_master_send(client, buf, 4)) != 4) {
+		pr_debug("%s: can't set alarm time\n", rs5c->rtc->name);
+		return -EIO;
+	}
+
+	/* ... and maybe enable its irq */
+	if (t->enabled) {
+		buf[0] = RS5C_ADDR(RS5C_REG_CTRL1);
+		buf[1] = rs5c->regs[RS5C_REG_CTRL1] | RS5C_CTRL1_AALE;
+		if ((i2c_master_send(client, buf, 2)) != 2)
+			printk(KERN_WARNING "%s: can't enable alarm\n",
+				rs5c->rtc->name);
+		rs5c->regs[RS5C_REG_CTRL1] = buf[1];
+	}
+
+	return 0;
+}
+
+#if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
+
 static int rs5c372_rtc_proc(struct device *dev, struct seq_file *seq)
 {
 	int err, osc, trim;
 
 	err = rs5c372_get_trim(to_i2c_client(dev), &osc, &trim);
 	if (err == 0) {
-		seq_printf(seq, "%d.%03d KHz\n", osc / 1000, osc % 1000);
-		seq_printf(seq, "trim\t: %d\n", trim);
+		seq_printf(seq, "crystal\t\t: %d.%03d KHz\n",
+				osc / 1000, osc % 1000);
+		seq_printf(seq, "trim\t\t: %d\n", trim);
 	}
 
 	return 0;
 }
 
+#else
+#define	rs5c372_rtc_proc	NULL
+#endif
+
 static const struct rtc_class_ops rs5c372_rtc_ops = {
 	.proc		= rs5c372_rtc_proc,
+	.ioctl		= rs5c_rtc_ioctl,
 	.read_time	= rs5c372_rtc_read_time,
 	.set_time	= rs5c372_rtc_set_time,
+	.read_alarm	= rs5c_read_alarm,
+	.set_alarm	= rs5c_set_alarm,
 };
+
+#if defined(CONFIG_RTC_INTF_SYSFS) || defined(CONFIG_RTC_INTF_SYSFS_MODULE)
 
 static ssize_t rs5c372_sysfs_show_trim(struct device *dev,
 				struct device_attribute *attr, char *buf)
···
 	if (err)
 		return err;
 
-	return sprintf(buf, "0x%2x\n", trim);
+	return sprintf(buf, "%d\n", trim);
 }
 static DEVICE_ATTR(trim, S_IRUGO, rs5c372_sysfs_show_trim, NULL);
 
···
 }
 static DEVICE_ATTR(osc, S_IRUGO, rs5c372_sysfs_show_osc, NULL);
 
-static int rs5c372_attach(struct i2c_adapter *adapter)
+static int rs5c_sysfs_register(struct device *dev)
 {
-	return i2c_probe(adapter, &addr_data, rs5c372_probe);
+	int err;
+
+	err = device_create_file(dev, &dev_attr_trim);
+	if (err)
+		return err;
+	err = device_create_file(dev, &dev_attr_osc);
+	if (err)
+		device_remove_file(dev, &dev_attr_trim);
+
+	return err;
 }
+
+#else
+static int rs5c_sysfs_register(struct device *dev)
+{
+	return 0;
+}
+#endif	/* SYSFS */
+
+static struct i2c_driver rs5c372_driver;
 
 static int rs5c372_probe(struct i2c_adapter *adapter, int address, int kind)
 {
 	int err = 0;
 	struct i2c_client *client;
 	struct rs5c372 *rs5c372;
+	struct rtc_time tm;
 
 	dev_dbg(adapter->class_dev.dev, "%s\n", __FUNCTION__);
 
···
 		err = -ENOMEM;
 		goto exit;
 	}
-	client = &rs5c372->client;
+
+	/* we read registers 0x0f then 0x00-0x0f; skip the first one */
+	rs5c372->regs=&rs5c372->buf[1];
+
+	/* On conversion to a "new style" i2c driver, we'll be handed
+	 * the i2c_client (we won't create it)
+	 */
+	client = &rs5c372->dev;
+	rs5c372->client = client;
 
 	/* I2C client */
 	client->addr = address;
···
 
 	i2c_set_clientdata(client, rs5c372);
 
-	rs5c372->msg[0].addr = address;
-	rs5c372->msg[0].flags = I2C_M_RD;
-	rs5c372->msg[0].len = sizeof(rs5c372->regs);
-	rs5c372->msg[0].buf = rs5c372->regs;
-
 	/* Inform the i2c layer */
 	if ((err = i2c_attach_client(client)))
 		goto exit_kfree;
 
-	dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
+	err = rs5c_get_regs(rs5c372);
+	if (err < 0)
+		goto exit_detach;
+
+	/* For "new style" drivers, irq is in i2c_client and chip type
+	 * info comes from i2c_client.dev.platform_data.  Meanwhile:
+	 *
+	 * STICK BOARD-SPECIFIC SETUP CODE RIGHT HERE
+	 */
+	if (rs5c372->type == rtc_undef) {
+		rs5c372->type = rtc_rs5c372b;
+		dev_warn(&client->dev, "assuming rs5c372b\n");
+	}
+
+	/* clock may be set for am/pm or 24 hr time */
+	switch (rs5c372->type) {
+	case rtc_rs5c372a:
+	case rtc_rs5c372b:
+		/* alarm uses ALARM_A; and nINTRA on 372a, nINTR on 372b.
+		 * so does periodic irq, except some 327a modes.
+		 */
+		if (rs5c372->regs[RS5C_REG_CTRL2] & RS5C372_CTRL2_24)
+			rs5c372->time24 = 1;
+		break;
+	case rtc_rv5c386:
+	case rtc_rv5c387a:
+		if (rs5c372->regs[RS5C_REG_CTRL1] & RV5C387_CTRL1_24)
+			rs5c372->time24 = 1;
+		/* alarm uses ALARM_W; and nINTRB for alarm and periodic
+		 * irq, on both 386 and 387
+		 */
+		break;
+	default:
+		dev_err(&client->dev, "unknown RTC type\n");
+		goto exit_detach;
+	}
+
+	/* if the oscillator lost power and no other software (like
+	 * the bootloader) set it up, do it here.
+	 */
+	if (rs5c372->regs[RS5C_REG_CTRL2] & RS5C_CTRL2_XSTP) {
+		unsigned char buf[3];
+
+		rs5c372->regs[RS5C_REG_CTRL2] &= ~RS5C_CTRL2_XSTP;
+
+		buf[0] = RS5C_ADDR(RS5C_REG_CTRL1);
+		buf[1] = rs5c372->regs[RS5C_REG_CTRL1];
+		buf[2] = rs5c372->regs[RS5C_REG_CTRL2];
+
+		/* use 24hr mode */
+		switch (rs5c372->type) {
+		case rtc_rs5c372a:
+		case rtc_rs5c372b:
+			buf[2] |= RS5C372_CTRL2_24;
+			rs5c372->time24 = 1;
+			break;
+		case rtc_rv5c386:
+		case rtc_rv5c387a:
+			buf[1] |= RV5C387_CTRL1_24;
+			rs5c372->time24 = 1;
+			break;
+		default:
+			/* impossible */
+			break;
+		}
+
+		if ((i2c_master_send(client, buf, 3)) != 3) {
+			dev_err(&client->dev, "setup error\n");
+			goto exit_detach;
+		}
+		rs5c372->regs[RS5C_REG_CTRL1] = buf[1];
+		rs5c372->regs[RS5C_REG_CTRL2] = buf[2];
+	}
+
+	if (rs5c372_get_datetime(client, &tm) < 0)
+		dev_warn(&client->dev, "clock needs to be set\n");
+
+	dev_info(&client->dev, "%s found, %s, driver version " DRV_VERSION "\n",
+			({ char *s; switch (rs5c372->type) {
+			case rtc_rs5c372a:	s = "rs5c372a"; break;
+			case rtc_rs5c372b:	s = "rs5c372b"; break;
+			case rtc_rv5c386:	s = "rv5c386"; break;
+			case rtc_rv5c387a:	s = "rv5c387a"; break;
+			default:		s = "chip"; break;
+			}; s;}),
+			rs5c372->time24 ? "24hr" : "am/pm"
+			);
+
+	/* FIXME when client->irq exists, use it to register alarm irq */
 
 	rs5c372->rtc = rtc_device_register(rs5c372_driver.driver.name,
 				&client->dev, &rs5c372_rtc_ops, THIS_MODULE);
···
 		goto exit_detach;
 	}
 
-	err = device_create_file(&client->dev, &dev_attr_trim);
+	err = rs5c_sysfs_register(&client->dev);
 	if (err)
 		goto exit_devreg;
-	err = device_create_file(&client->dev, &dev_attr_osc);
-	if (err)
-		goto exit_trim;
 
 	return 0;
-
-exit_trim:
-	device_remove_file(&client->dev, &dev_attr_trim);
 
 exit_devreg:
 	rtc_device_unregister(rs5c372->rtc);
···
 	return err;
 }
 
+static int rs5c372_attach(struct i2c_adapter *adapter)
+{
+	return i2c_probe(adapter, &addr_data, rs5c372_probe);
+}
+
 static int rs5c372_detach(struct i2c_client *client)
 {
 	int err;
···
 	if (rs5c372->rtc)
 		rtc_device_unregister(rs5c372->rtc);
 
+	/* REVISIT properly destroy the sysfs files ... */
+
 	if ((err = i2c_detach_client(client)))
 		return err;
 
 	kfree(rs5c372);
 	return 0;
 }
+
+static struct i2c_driver rs5c372_driver = {
+	.driver		= {
+		.name	= "rtc-rs5c372",
+	},
+	.attach_adapter	= &rs5c372_attach,
+	.detach_client	= &rs5c372_detach,
+};
 
 static __init int rs5c372_init(void)
 {