[PATCH 0/3] i2c: add at24 eeprom support

[PATCH 0/3] i2c: add at24 eeprom support

[Jean-Christophe PLAGNIOL-VILLARD]

HI,

	this patch serie add the at24 eeprom support based on linux 3.6

	the depends on the i2c prepare 1t24 support patch series

The following changes since commit 5526278ac77ecd7109c9c1bbc35d7c74875902e7:

  i2c: add id_table support (2012-11-03 13:33:54 +0800)

are available in the git repository at:

  git://git.jcrosoft.org/barebox.git delivery/at24

for you to fetch changes up to fe6968e20c39461df068d5cc15869012be4a3161:

  eeprom: add at24 support (2012-11-03 13:46:50 +0800)

----------------------------------------------------------------
Jean-Christophe PLAGNIOL-VILLARD (3):
      import log2 support from linux
      add roundup and rounddown support
      eeprom: add at24 support

 drivers/eeprom/Kconfig  |   19 ++++++++++
 drivers/eeprom/Makefile |    1 +
 drivers/eeprom/at24.c   |  460 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/i2c/at24.h      |   35 +++++++++++++++++++
 include/linux/kernel.h  |   15 ++++++++
 include/linux/log2.h    |  190 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 720 insertions(+)
 create mode 100644 drivers/eeprom/at24.c
 create mode 100644 include/i2c/at24.h
 create mode 100644 include/linux/log2.h

Best Regards,
J.

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[PATCH 1/3] import log2 support from linux

[Jean-Christophe PLAGNIOL-VILLARD]

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
---
 include/linux/log2.h |  190 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 190 insertions(+)
 create mode 100644 include/linux/log2.h

diff --git a/include/linux/log2.h b/include/linux/log2.h
new file mode 100644
index 0000000..389043a
--- /dev/null
+++ b/include/linux/log2.h
@@ -0,0 +1,190 @@
+/* Integer base 2 logarithm calculation
+ *
+ * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_LOG2_H
+#define _LINUX_LOG2_H
+
+#include <linux/types.h>
+#include <linux/bitops.h>
+
+/*
+ * deal with unrepresentable constant logarithms
+ */
+extern __attribute__((const, noreturn))
+int ____ilog2_NaN(void);
+
+/*
+ * non-constant log of base 2 calculators
+ * - the arch may override these in asm/bitops.h if they can be implemented
+ *   more efficiently than using fls() and fls64()
+ * - the arch is not required to handle n==0 if implementing the fallback
+ */
+#ifndef CONFIG_ARCH_HAS_ILOG2_U32
+static inline __attribute__((const))
+int __ilog2_u32(u32 n)
+{
+	return fls(n) - 1;
+}
+#endif
+
+#ifndef CONFIG_ARCH_HAS_ILOG2_U64
+static inline __attribute__((const))
+int __ilog2_u64(u64 n)
+{
+	return fls64(n) - 1;
+}
+#endif
+
+/*
+ *  Determine whether some value is a power of two, where zero is
+ * *not* considered a power of two.
+ */
+
+static inline __attribute__((const))
+bool is_power_of_2(unsigned long n)
+{
+	return (n != 0 && ((n & (n - 1)) == 0));
+}
+
+/**
+ * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
+ * @n - parameter
+ *
+ * constant-capable log of base 2 calculation
+ * - this can be used to initialise global variables from constant data, hence
+ *   the massive ternary operator construction
+ *
+ * selects the appropriately-sized optimised version depending on sizeof(n)
+ */
+#define ilog2(n)				\
+(						\
+	__builtin_constant_p(n) ? (		\
+		(n) < 1 ? ____ilog2_NaN() :	\
+		(n) & (1ULL << 63) ? 63 :	\
+		(n) & (1ULL << 62) ? 62 :	\
+		(n) & (1ULL << 61) ? 61 :	\
+		(n) & (1ULL << 60) ? 60 :	\
+		(n) & (1ULL << 59) ? 59 :	\
+		(n) & (1ULL << 58) ? 58 :	\
+		(n) & (1ULL << 57) ? 57 :	\
+		(n) & (1ULL << 56) ? 56 :	\
+		(n) & (1ULL << 55) ? 55 :	\
+		(n) & (1ULL << 54) ? 54 :	\
+		(n) & (1ULL << 53) ? 53 :	\
+		(n) & (1ULL << 52) ? 52 :	\
+		(n) & (1ULL << 51) ? 51 :	\
+		(n) & (1ULL << 50) ? 50 :	\
+		(n) & (1ULL << 49) ? 49 :	\
+		(n) & (1ULL << 48) ? 48 :	\
+		(n) & (1ULL << 47) ? 47 :	\
+		(n) & (1ULL << 46) ? 46 :	\
+		(n) & (1ULL << 45) ? 45 :	\
+		(n) & (1ULL << 44) ? 44 :	\
+		(n) & (1ULL << 43) ? 43 :	\
+		(n) & (1ULL << 42) ? 42 :	\
+		(n) & (1ULL << 41) ? 41 :	\
+		(n) & (1ULL << 40) ? 40 :	\
+		(n) & (1ULL << 39) ? 39 :	\
+		(n) & (1ULL << 38) ? 38 :	\
+		(n) & (1ULL << 37) ? 37 :	\
+		(n) & (1ULL << 36) ? 36 :	\
+		(n) & (1ULL << 35) ? 35 :	\
+		(n) & (1ULL << 34) ? 34 :	\
+		(n) & (1ULL << 33) ? 33 :	\
+		(n) & (1ULL << 32) ? 32 :	\
+		(n) & (1ULL << 31) ? 31 :	\
+		(n) & (1ULL << 30) ? 30 :	\
+		(n) & (1ULL << 29) ? 29 :	\
+		(n) & (1ULL << 28) ? 28 :	\
+		(n) & (1ULL << 27) ? 27 :	\
+		(n) & (1ULL << 26) ? 26 :	\
+		(n) & (1ULL << 25) ? 25 :	\
+		(n) & (1ULL << 24) ? 24 :	\
+		(n) & (1ULL << 23) ? 23 :	\
+		(n) & (1ULL << 22) ? 22 :	\
+		(n) & (1ULL << 21) ? 21 :	\
+		(n) & (1ULL << 20) ? 20 :	\
+		(n) & (1ULL << 19) ? 19 :	\
+		(n) & (1ULL << 18) ? 18 :	\
+		(n) & (1ULL << 17) ? 17 :	\
+		(n) & (1ULL << 16) ? 16 :	\
+		(n) & (1ULL << 15) ? 15 :	\
+		(n) & (1ULL << 14) ? 14 :	\
+		(n) & (1ULL << 13) ? 13 :	\
+		(n) & (1ULL << 12) ? 12 :	\
+		(n) & (1ULL << 11) ? 11 :	\
+		(n) & (1ULL << 10) ? 10 :	\
+		(n) & (1ULL <<  9) ?  9 :	\
+		(n) & (1ULL <<  8) ?  8 :	\
+		(n) & (1ULL <<  7) ?  7 :	\
+		(n) & (1ULL <<  6) ?  6 :	\
+		(n) & (1ULL <<  5) ?  5 :	\
+		(n) & (1ULL <<  4) ?  4 :	\
+		(n) & (1ULL <<  3) ?  3 :	\
+		(n) & (1ULL <<  2) ?  2 :	\
+		(n) & (1ULL <<  1) ?  1 :	\
+		(n) & (1ULL <<  0) ?  0 :	\
+		____ilog2_NaN()			\
+				   ) :		\
+	(sizeof(n) <= 4) ?			\
+	__ilog2_u32(n) :			\
+	__ilog2_u64(n)				\
+ )
+
+/**
+ * roundup_pow_of_two - round the given value up to nearest power of two
+ * @n - parameter
+ *
+ * round the given value up to the nearest power of two
+ * - the result is undefined when n == 0
+ * - this can be used to initialise global variables from constant data
+ */
+#define roundup_pow_of_two(n)			\
+(						\
+	__builtin_constant_p(n) ? (		\
+		(n == 1) ? 1 :			\
+		(1UL << (ilog2((n) - 1) + 1))	\
+				   ) :		\
+	__roundup_pow_of_two(n)			\
+ )
+
+/**
+ * rounddown_pow_of_two - round the given value down to nearest power of two
+ * @n - parameter
+ *
+ * round the given value down to the nearest power of two
+ * - the result is undefined when n == 0
+ * - this can be used to initialise global variables from constant data
+ */
+#define rounddown_pow_of_two(n)			\
+(						\
+	__builtin_constant_p(n) ? (		\
+		(1UL << ilog2(n))) :		\
+	__rounddown_pow_of_two(n)		\
+ )
+
+/**
+ * order_base_2 - calculate the (rounded up) base 2 order of the argument
+ * @n: parameter
+ *
+ * The first few values calculated by this routine:
+ *  ob2(0) = 0
+ *  ob2(1) = 0
+ *  ob2(2) = 1
+ *  ob2(3) = 2
+ *  ob2(4) = 2
+ *  ob2(5) = 3
+ *  ... and so on.
+ */
+
+#define order_base_2(n) ilog2(roundup_pow_of_two(n))
+
+#endif /* _LINUX_LOG2_H */
-- 
1.7.10.4


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[PATCH 2/3] add roundup and rounddown support

[Jean-Christophe PLAGNIOL-VILLARD]

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
---
 include/linux/kernel.h |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index e9e2f07..92c3391 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -90,5 +90,20 @@
 	__val = __val < __min ? __min: __val;	\
 	__val > __max ? __max: __val; })
 
+
+/* The `const' in roundup() prevents gcc-3.3 from calling __divdi3 */
+#define roundup(x, y) (					\
+{							\
+	const typeof(y) __y = y;			\
+	(((x) + (__y - 1)) / __y) * __y;		\
+}							\
+)
+#define rounddown(x, y) (				\
+{							\
+	typeof(x) __x = (x);				\
+	__x - (__x % (y));				\
+}							\
+)
+
 #endif /* _LINUX_KERNEL_H */
 
-- 
1.7.10.4


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[PATCH 3/3] eeprom: add at24 support

[Jean-Christophe PLAGNIOL-VILLARD]

This driver to get read/write support to most I2C EEPROMs,
after you configure the driver to know about each EEPROM on
your target board.  Use these generic chip names, instead of
vendor-specific ones like at24c64 or 24lc02:

   24c00, 24c01, 24c02, spd (readonly 24c02), 24c04, 24c08,
   24c16, 24c32, 24c64, 24c128, 24c256, 24c512, 24c1024

Unless you like data loss puzzles, always be sure that any chip
you configure as a 24c32 (32 kbit) or larger is NOT really a
24c16 (16 kbit) or smaller, and vice versa. Marking the chip
as read-only won't help recover from this. Also, if your chip
has any software write-protect mechanism you may want to review the
code to make sure this driver won't turn it on by accident.

Based on linux 3.6

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
---
 drivers/eeprom/Kconfig  |   19 ++
 drivers/eeprom/Makefile |    1 +
 drivers/eeprom/at24.c   |  460 +++++++++++++++++++++++++++++++++++++++++++++++
 include/i2c/at24.h      |   35 ++++
 4 files changed, 515 insertions(+)
 create mode 100644 drivers/eeprom/at24.c
 create mode 100644 include/i2c/at24.h

diff --git a/drivers/eeprom/Kconfig b/drivers/eeprom/Kconfig
index a0b5489..ce9cfe7 100644
--- a/drivers/eeprom/Kconfig
+++ b/drivers/eeprom/Kconfig
@@ -8,4 +8,23 @@ config EEPROM_AT25
 	  after you configure the board init code to know about each eeprom
 	  on your target board.
 
+config EEPROM_AT24
+	bool "at24 based eeprom"
+	depends on I2C
+	help
+	  Enable this driver to get read/write support to most I2C EEPROMs,
+	  after you configure the driver to know about each EEPROM on
+	  your target board.  Use these generic chip names, instead of
+	  vendor-specific ones like at24c64 or 24lc02:
+
+	     24c00, 24c01, 24c02, spd (readonly 24c02), 24c04, 24c08,
+	     24c16, 24c32, 24c64, 24c128, 24c256, 24c512, 24c1024
+
+	  Unless you like data loss puzzles, always be sure that any chip
+	  you configure as a 24c32 (32 kbit) or larger is NOT really a
+	  24c16 (16 kbit) or smaller, and vice versa. Marking the chip
+	  as read-only won't help recover from this. Also, if your chip
+	  has any software write-protect mechanism you may want to review the
+	  code to make sure this driver won't turn it on by accident.
+
 endmenu
diff --git a/drivers/eeprom/Makefile b/drivers/eeprom/Makefile
index e323bd0..e287eb0 100644
--- a/drivers/eeprom/Makefile
+++ b/drivers/eeprom/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_EEPROM_AT25)	+= at25.o
+obj-$(CONFIG_EEPROM_AT24)	+= at24.o
diff --git a/drivers/eeprom/at24.c b/drivers/eeprom/at24.c
new file mode 100644
index 0000000..6f0133a
--- /dev/null
+++ b/drivers/eeprom/at24.c
@@ -0,0 +1,460 @@
+/*
+ * at24.c - handle most I2C EEPROMs
+ *
+ * Copyright (C) 2005-2007 David Brownell
+ * Copyright (C) 2008 Wolfram Sang, Pengutronix
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <common.h>
+#include <init.h>
+#include <malloc.h>
+#include <clock.h>
+#include <driver.h>
+#include <xfuncs.h>
+#include <errno.h>
+#include <linux/math64.h>
+#include <linux/log2.h>
+#include <i2c/i2c.h>
+#include <i2c/at24.h>
+
+/*
+ * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
+ * Differences between different vendor product lines (like Atmel AT24C or
+ * MicroChip 24LC, etc) won't much matter for typical read/write access.
+ * There are also I2C RAM chips, likewise interchangeable. One example
+ * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
+ *
+ * However, misconfiguration can lose data. "Set 16-bit memory address"
+ * to a part with 8-bit addressing will overwrite data. Writing with too
+ * big a page size also loses data. And it's not safe to assume that the
+ * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
+ * uses 0x51, for just one example.
+ *
+ * So this driver uses "new style" I2C driver binding, expecting to be
+ * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
+ * similar kernel-resident tables; or, configuration data coming from
+ * a bootloader.
+ *
+ * Other than binding model, current differences from "eeprom" driver are
+ * that this one handles write access and isn't restricted to 24c02 devices.
+ * It also handles larger devices (32 kbit and up) with two-byte addresses,
+ * which won't work on pure SMBus systems.
+ */
+
+struct at24_data {
+	struct at24_platform_data chip;
+
+	struct cdev		cdev;
+	struct file_operations	fops;
+
+	u8 *writebuf;
+	unsigned write_max;
+	unsigned num_addresses;
+
+	/*
+	 * Some chips tie up multiple I2C addresses; dummy devices reserve
+	 * them for us.
+	 */
+	struct i2c_client *client[];
+};
+
+/*
+ * This parameter is to help this driver avoid blocking other drivers out
+ * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
+ * clock, one 256 byte read takes about 1/43 second which is excessive;
+ * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
+ * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
+ *
+ * This value is forced to be a power of two so that writes align on pages.
+ */
+static unsigned io_limit = 128;
+
+/*
+ * Specs often allow 5 msec for a page write, sometimes 20 msec;
+ * it's important to recover from write timeouts.
+ */
+static unsigned write_timeout = 25;
+
+#define AT24_SIZE_BYTELEN 5
+#define AT24_SIZE_FLAGS 8
+
+#define AT24_BITMASK(x) (BIT(x) - 1)
+
+/* create non-zero magic value for given eeprom parameters */
+#define AT24_DEVICE_MAGIC(_len, _flags) 		\
+	((1 << AT24_SIZE_FLAGS | (_flags)) 		\
+	    << AT24_SIZE_BYTELEN | ilog2(_len))
+
+static struct platform_device_id at24_ids[] = {
+	/* needs 8 addresses as A0-A2 are ignored */
+	{ "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
+	/* old variants can't be handled with this generic entry! */
+	{ "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
+	{ "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
+	/* spd is a 24c02 in memory DIMMs */
+	{ "spd", AT24_DEVICE_MAGIC(2048 / 8,
+		AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
+	{ "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
+	/* 24rf08 quirk is handled at i2c-core */
+	{ "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
+	{ "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
+	{ "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
+	{ "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
+	{ "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
+	{ "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
+	{ "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
+	{ "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
+	{ "at24", 0 },
+	{ /* END OF LIST */ }
+};
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * This routine supports chips which consume multiple I2C addresses. It
+ * computes the addressing information to be used for a given r/w request.
+ * Assumes that sanity checks for offset happened at sysfs-layer.
+ */
+static struct i2c_client *at24_translate_offset(struct at24_data *at24,
+		unsigned *offset)
+{
+	unsigned i;
+
+	if (at24->chip.flags & AT24_FLAG_ADDR16) {
+		i = *offset >> 16;
+		*offset &= 0xffff;
+	} else {
+		i = *offset >> 8;
+		*offset &= 0xff;
+	}
+
+	return at24->client[i];
+}
+
+static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
+		unsigned offset, size_t count)
+{
+	struct i2c_msg msg[2];
+	u8 msgbuf[2];
+	struct i2c_client *client;
+	int status, i;
+	uint64_t start, read_time;
+
+	memset(msg, 0, sizeof(msg));
+
+	/*
+	 * REVISIT some multi-address chips don't rollover page reads to
+	 * the next slave address, so we may need to truncate the count.
+	 * Those chips might need another quirk flag.
+	 *
+	 * If the real hardware used four adjacent 24c02 chips and that
+	 * were misconfigured as one 24c08, that would be a similar effect:
+	 * one "eeprom" file not four, but larger reads would fail when
+	 * they crossed certain pages.
+	 */
+
+	/*
+	 * Slave address and byte offset derive from the offset. Always
+	 * set the byte address; on a multi-master board, another master
+	 * may have changed the chip's "current" address pointer.
+	 */
+	client = at24_translate_offset(at24, &offset);
+
+	if (count > io_limit)
+		count = io_limit;
+
+	i = 0;
+	if (at24->chip.flags & AT24_FLAG_ADDR16)
+		msgbuf[i++] = offset >> 8;
+	msgbuf[i++] = offset;
+
+	msg[0].addr = client->addr;
+	msg[0].buf = msgbuf;
+	msg[0].len = i;
+
+	msg[1].addr = client->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].buf = buf;
+	msg[1].len = count;
+
+	/*
+	 * Reads fail if the previous write didn't complete yet. We may
+	 * loop a few times until this one succeeds, waiting at least
+	 * long enough for one entire page write to work.
+	 */
+	start = get_time_ns();
+	do {
+		read_time = get_time_ns();
+		status = i2c_transfer(client->adapter, msg, 2);
+		if (status == 2)
+			status = count;
+		dev_dbg(&client->dev, "read %zu@%d --> %d (%llu)\n",
+				count, offset, status, read_time);
+
+		if (status == count)
+			return count;
+
+		/* REVISIT: at HZ=100, this is sloooow */
+		mdelay(1);
+	} while (!is_timeout(start, write_timeout * MSECOND));
+
+	return -ETIMEDOUT;
+}
+
+static ssize_t at24_read(struct at24_data *at24,
+		char *buf, loff_t off, size_t count)
+{
+	ssize_t retval = 0;
+
+	if (unlikely(!count))
+		return count;
+
+	/*
+	 * Read data from chip, protecting against concurrent updates
+	 * from this host, but not from other I2C masters.
+	 */
+	while (count) {
+		ssize_t	status;
+
+		status = at24_eeprom_read(at24, buf, off, count);
+		if (status <= 0) {
+			if (retval == 0)
+				retval = status;
+			break;
+		}
+		buf += status;
+		off += status;
+		count -= status;
+		retval += status;
+	}
+
+	return retval;
+}
+
+static ssize_t at24_cdev_read(struct cdev *cdev, void *buf, size_t count,
+		loff_t off, ulong flags)
+{
+	struct at24_data *at24 = cdev->priv;
+
+	return at24_read(at24, buf, off, count);
+}
+
+/*
+ * Note that if the hardware write-protect pin is pulled high, the whole
+ * chip is normally write protected. But there are plenty of product
+ * variants here, including OTP fuses and partial chip protect.
+ *
+ * We only use page mode writes; the alternative is sloooow. This routine
+ * writes at most one page.
+ */
+static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
+		unsigned offset, size_t count)
+{
+	struct i2c_client *client;
+	struct i2c_msg msg;
+	ssize_t status;
+	uint64_t start, write_time;
+	unsigned next_page;
+	int i = 0;
+
+	/* Get corresponding I2C address and adjust offset */
+	client = at24_translate_offset(at24, &offset);
+
+	/* write_max is at most a page */
+	if (count > at24->write_max)
+		count = at24->write_max;
+
+	/* Never roll over backwards, to the start of this page */
+	next_page = roundup(offset + 1, at24->chip.page_size);
+	if (offset + count > next_page)
+		count = next_page - offset;
+
+
+	msg.addr = client->addr;
+	msg.flags = 0;
+
+	/* msg.buf is u8 and casts will mask the values */
+	msg.buf = at24->writebuf;
+	if (at24->chip.flags & AT24_FLAG_ADDR16)
+		msg.buf[i++] = offset >> 8;
+
+	msg.buf[i++] = offset;
+	memcpy(&msg.buf[i], buf, count);
+	msg.len = i + count;
+
+	/*
+	 * Writes fail if the previous one didn't complete yet. We may
+	 * loop a few times until this one succeeds, waiting at least
+	 * long enough for one entire page write to work.
+	 */
+	start = get_time_ns();
+	do {
+		write_time = get_time_ns();
+		status = i2c_transfer(client->adapter, &msg, 1);
+		if (status == 1)
+			status = count;
+		dev_dbg(&client->dev, "write %zu@%d --> %zd (%llu)\n",
+				count, offset, status, write_time);
+
+		if (status == count)
+			return count;
+
+		/* REVISIT: at HZ=100, this is sloooow */
+		mdelay(1);
+	} while (!is_timeout(start, write_timeout * MSECOND));
+
+	return -ETIMEDOUT;
+}
+
+static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
+			  size_t count)
+{
+	ssize_t retval = 0;
+
+	if (unlikely(!count))
+		return count;
+
+	while (count) {
+		ssize_t	status;
+
+		status = at24_eeprom_write(at24, buf, off, count);
+		if (status <= 0) {
+			if (retval == 0)
+				retval = status;
+			break;
+		}
+		buf += status;
+		off += status;
+		count -= status;
+		retval += status;
+	}
+
+	return retval;
+}
+
+static ssize_t at24_cdev_write(struct cdev *cdev, const void *buf, size_t count,
+		loff_t off, ulong flags)
+{
+	struct at24_data *at24 = cdev->priv;
+
+	return at24_write(at24, buf, off, count);
+}
+
+static int at24_probe(struct device_d *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct at24_platform_data chip;
+	bool writable;
+	struct at24_data *at24;
+	int err;
+	unsigned i, num_addresses;
+
+	if (dev->platform_data) {
+		chip = *(struct at24_platform_data *)dev->platform_data;
+	} else {
+		unsigned long magic;
+
+		err = dev_get_drvdata(dev, (unsigned long *)&magic);
+		if (err)
+			return err;
+
+		chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
+		magic >>= AT24_SIZE_BYTELEN;
+		chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
+		/*
+		 * This is slow, but we can't know all eeproms, so we better
+		 * play safe. Specifying custom eeprom-types via platform_data
+		 * is recommended anyhow.
+		 */
+		chip.page_size = 1;
+	}
+
+	if (!is_power_of_2(chip.byte_len))
+		dev_warn(&client->dev,
+			"byte_len looks suspicious (no power of 2)!\n");
+	if (!chip.page_size) {
+		dev_err(&client->dev, "page_size must not be 0!\n");
+		err = -EINVAL;
+		goto err_out;
+	}
+	if (!is_power_of_2(chip.page_size))
+		dev_warn(&client->dev,
+			"page_size looks suspicious (no power of 2)!\n");
+
+	if (chip.flags & AT24_FLAG_TAKE8ADDR)
+		num_addresses = 8;
+	else
+		num_addresses =	DIV_ROUND_UP(chip.byte_len,
+			(chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
+
+	at24 = xzalloc(sizeof(struct at24_data) +
+		num_addresses * sizeof(struct i2c_client *));
+
+	at24->chip = chip;
+	at24->num_addresses = num_addresses;
+	at24->cdev.name = asprintf("eeprom%d", dev->id);
+	at24->cdev.priv = at24;
+	at24->cdev.dev = dev;
+	at24->cdev.ops = &at24->fops;
+	at24->fops.lseek = dev_lseek_default;
+	at24->fops.read	= at24_cdev_read,
+	at24->cdev.size = chip.byte_len;
+
+	writable = !(chip.flags & AT24_FLAG_READONLY);
+	if (writable) {
+		unsigned write_max = chip.page_size;
+
+		at24->fops.write = at24_cdev_write;
+
+		if (write_max > io_limit)
+			write_max = io_limit;
+		at24->write_max = write_max;
+
+		/* buffer (data + address at the beginning) */
+		at24->writebuf = xmalloc(write_max + 2);
+	}
+
+	at24->client[0] = client;
+
+	/* use dummy devices for multiple-address chips */
+	for (i = 1; i < num_addresses; i++) {
+		at24->client[i] = i2c_new_dummy(client->adapter,
+					client->addr + i);
+		if (!at24->client[i]) {
+			dev_err(&client->dev, "address 0x%02x unavailable\n",
+					client->addr + i);
+			err = -EADDRINUSE;
+			goto err_clients;
+		}
+	}
+
+	devfs_create(&at24->cdev);
+
+	return 0;
+
+err_clients:
+	kfree(at24->writebuf);
+	kfree(at24);
+err_out:
+	dev_dbg(&client->dev, "probe error %d\n", err);
+	return err;
+
+}
+
+static struct driver_d at24_driver = {
+	.name		= "at24",
+	.probe		= at24_probe,
+	.id_table	= at24_ids,
+};
+
+static int at24_init(void)
+{
+	i2c_register_driver(&at24_driver);
+	return 0;
+}
+device_initcall(at24_init);
diff --git a/include/i2c/at24.h b/include/i2c/at24.h
new file mode 100644
index 0000000..1013308
--- /dev/null
+++ b/include/i2c/at24.h
@@ -0,0 +1,35 @@
+/*
+ * at24.h - platform_data for the at24 (generic eeprom) driver
+ * (C) Copyright 2008 by Pengutronix
+ * (C) Copyright 2012 by Wolfram Sang
+ * same license as the driver
+ */
+
+#ifndef _LINUX_AT24_H
+#define _LINUX_AT24_H
+
+#include <linux/types.h>
+
+/**
+ * struct at24_platform_data - data to set up at24 (generic eeprom) driver
+ * @byte_len: size of eeprom in byte
+ * @page_size: number of byte which can be written in one go
+ * @flags: tunable options, check AT24_FLAG_* defines
+ *
+ * If you set up a custom eeprom type, please double-check the parameters.
+ * Especially page_size needs extra care, as you risk data loss if your value
+ * is bigger than what the chip actually supports!
+ *
+ */
+
+struct at24_platform_data {
+	u32		byte_len;		/* size (sum of all addr) */
+	u16		page_size;		/* for writes */
+	u8		flags;
+#define AT24_FLAG_ADDR16	0x80	/* address pointer is 16 bit */
+#define AT24_FLAG_READONLY	0x40	/* sysfs-entry will be read-only */
+#define AT24_FLAG_IRUGO		0x20	/* sysfs-entry will be world-readable */
+#define AT24_FLAG_TAKE8ADDR	0x10	/* take always 8 addresses (24c00) */
+};
+
+#endif /* _LINUX_AT24_H */
-- 
1.7.10.4


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Re: [PATCH 0/3] i2c: add at24 eeprom support

[Sascha Hauer]

On Sat, Nov 03, 2012 at 09:56:55PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> HI,
> 
> 	this patch serie add the at24 eeprom support based on linux 3.6
> 
> 	the depends on the i2c prepare 1t24 support patch series
> 
> The following changes since commit 5526278ac77ecd7109c9c1bbc35d7c74875902e7:
> 
>   i2c: add id_table support (2012-11-03 13:33:54 +0800)
> 
> are available in the git repository at:
> 
>   git://git.jcrosoft.org/barebox.git delivery/at24
> 
> for you to fetch changes up to fe6968e20c39461df068d5cc15869012be4a3161:

Applied, thanks

Sascha

> 
>   eeprom: add at24 support (2012-11-03 13:46:50 +0800)
> 
> ----------------------------------------------------------------
> Jean-Christophe PLAGNIOL-VILLARD (3):
>       import log2 support from linux
>       add roundup and rounddown support
>       eeprom: add at24 support
> 
>  drivers/eeprom/Kconfig  |   19 ++++++++++
>  drivers/eeprom/Makefile |    1 +
>  drivers/eeprom/at24.c   |  460 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/i2c/at24.h      |   35 +++++++++++++++++++
>  include/linux/kernel.h  |   15 ++++++++
>  include/linux/log2.h    |  190 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 720 insertions(+)
>  create mode 100644 drivers/eeprom/at24.c
>  create mode 100644 include/i2c/at24.h
>  create mode 100644 include/linux/log2.h
> 
> Best Regards,
> J.
> 
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox
> 

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