New-style I2C and SMBus EEPROM driver (with device_ids) Add a new-style driver for most I2C EEPROMs, giving sysfs read/write access to their data. Tested with various chips and clock rates.
Signed-off-by: Wolfram Sang <[EMAIL PROTECTED]>
---
Note: I am not in my office this week, so I can't do all the tests I usually
do. Please check carefully! David: I hope it is OK with you that I added myself
as another author of this module.
Updates since last version:
- added device_ids for common eeprom types (parameters encoded in
a 'magic' driver_data value)
- removed platform_data entry 'i2c_addr_mask' and calculated
its value from other parameters
- added 24c00-quirk flag (it covers 8 addresses)
- added a flag to make eeproms world-readable (used for spd)
- rewrote code that adds an i2c-address to an i2c-message
- rewrote code which truncates to page_size
- removed 'addr'-variable from eeprom-functions; i2c-address is
now taken from the corresponding client-structure
- write buffer now allocated once in probe
- removed some sanity checks for file offsets as they are handled at
the sysfs-layer already.
- fixed typos and corrected spellings in comments and Kconfig
- renamed some functions to be more self-explanatory
- added includes
- further cleanups and simplifications
- added myself as another author
Updates since last version:
- revisited includes
- made write-timeout a module parameter
- array of clients is allocated dynamically
- removed unnecessary indentation within code
- formatted comments
- replaced at24_ee_address with a simpler function
- at24_ee_write now really waits till timeout
- added simple checks of provided eeprom chip data in at24_probe
- added comment in at24.h about double-checking custom data
- minor fixes
Updates in this version:
- move chip data out of the driver into a seperate .h-file
- prefix defined constants with AT24_
- make bin file readonly if requested by flags
- introduce AT24_MAX_CLIENTS
- bugfix: check correct retval in at24_ee_write
drivers/i2c/chips/Kconfig | 26 ++
drivers/i2c/chips/Makefile | 1
drivers/i2c/chips/at24.c | 574 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/i2c/at24.h | 104 ++++++++
4 files changed, 705 insertions(+)
create mode 100644 drivers/i2c/chips/at24.c
create mode 100644 include/linux/i2c/at24.h
Index: linux-2.6.26-rc4/drivers/i2c/chips/Kconfig
===================================================================
--- linux-2.6.26-rc4.orig/drivers/i2c/chips/Kconfig
+++ linux-2.6.26-rc4/drivers/i2c/chips/Kconfig
@@ -14,6 +14,32 @@
This driver can also be built as a module. If so, the module
will be called ds1682.
+config I2C_AT24
+ tristate "EEPROMs from most vendors"
+ depends on SYSFS && EXPERIMENTAL
+ 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.
+
+ If you use this with an SMBus adapter instead of an I2C adapter,
+ full functionality is not availble. Only smaller devices are
+ supported (24c16 and below, max 4 kByte).
+
+ This driver can also be built as a module. If so, the module
+ will be called at24.
+
config SENSORS_EEPROM
tristate "EEPROM reader"
depends on EXPERIMENTAL
Index: linux-2.6.26-rc4/drivers/i2c/chips/Makefile
===================================================================
--- linux-2.6.26-rc4.orig/drivers/i2c/chips/Makefile
+++ linux-2.6.26-rc4/drivers/i2c/chips/Makefile
@@ -10,6 +10,7 @@
#
obj-$(CONFIG_DS1682) += ds1682.o
+obj-$(CONFIG_I2C_AT24) += at24.o
obj-$(CONFIG_SENSORS_EEPROM) += eeprom.o
obj-$(CONFIG_SENSORS_MAX6875) += max6875.o
obj-$(CONFIG_SENSORS_PCA9539) += pca9539.o
Index: linux-2.6.26-rc4/drivers/i2c/chips/at24.c
===================================================================
--- /dev/null
+++ linux-2.6.26-rc4/drivers/i2c/chips/at24.c
@@ -0,0 +1,574 @@
+/*
+ * 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 <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+#include <linux/mod_devicetable.h>
+#include <linux/log2.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/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.
+ *
+ * Accordingly, explicit board-specific configuration data should be used
+ * in almost all cases. (One partial exception is an SMBus used to access
+ * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
+ *
+ * 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;
+ bool use_smbus;
+
+ /*
+ * Lock protects against activities from other Linux tasks,
+ * but not from changes by other I2C masters.
+ */
+ struct mutex lock;
+ struct bin_attribute bin;
+
+ u8 *writebuf;
+ unsigned write_max;
+ unsigned num_addresses;
+
+ /*
+ * Some chips tie up multiple I2C addresses; dummy devices reserve
+ * them for us, and we'll use them with SMBus calls.
+ */
+ 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;
+module_param(io_limit, uint, 0);
+MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 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;
+module_param(write_timeout, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * 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 = 0;
+
+ 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 misconfiged 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;
+
+ /* Smaller eproms can work given some SMBus extension calls */
+ if (at24->use_smbus) {
+ if (count > I2C_SMBUS_BLOCK_MAX)
+ count = I2C_SMBUS_BLOCK_MAX;
+ status = i2c_smbus_read_i2c_block_data(client, offset,
+ count, buf);
+ dev_dbg(&client->dev, "smbus read [EMAIL PROTECTED] --> %d\n",
+ count, offset, status);
+ return (status < 0) ? -EIO : status;
+ }
+
+ /*
+ * When we have a better choice than SMBus calls, use a combined
+ * I2C message. Write address; then read up to io_limit data bytes.
+ * Note that read page rollover helps us here (unlike writes).
+ * msgbuf is u8 and will cast to our needs.
+ */
+ 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;
+
+ status = i2c_transfer(client->adapter, msg, 2);
+ dev_dbg(&client->dev, "i2c read [EMAIL PROTECTED] --> %d\n",
+ count, offset, status);
+
+ if (status == 2)
+ return count;
+ else if (status >= 0)
+ return -EIO;
+ else
+ return status;
+}
+
+static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ struct at24_data *at24;
+ ssize_t retval = 0;
+
+ at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
+
+ if (unlikely(!count))
+ return count;
+
+ /*
+ * Read data from chip, protecting against concurrent updates
+ * from this host ... but not from other i2c masters.
+ */
+ mutex_lock(&at24->lock);
+
+ 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;
+ }
+
+ mutex_unlock(&at24->lock);
+
+ return retval;
+}
+
+
+/*
+ * REVISIT: export at24_bin{read,write}() to let other kernel code use
+ * eeprom data. For example, it might hold a board's Ethernet address, or
+ * board-specific calibration data generated on the manufacturing floor.
+ */
+
+
+/*
+ * 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, char *buf,
+ unsigned offset, size_t count)
+{
+ struct i2c_client *client;
+ struct i2c_msg msg;
+ ssize_t status;
+ unsigned long timeout, write_time;
+ unsigned next_page;
+
+ /* 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;
+
+ /* If we'll use i2c calls for I/O, set up the message */
+ if (!at24->use_smbus) {
+ int i = 0;
+
+ 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.
+ */
+ timeout = jiffies + msecs_to_jiffies(write_timeout);
+ do {
+ write_time = jiffies;
+ if (at24->use_smbus) {
+ status = i2c_smbus_write_i2c_block_data(client,
+ offset, count, buf);
+ if (status == 0)
+ status = count;
+ } else {
+ status = i2c_transfer(client->adapter, &msg, 1);
+ if (status == 1)
+ status = count;
+ }
+ dev_dbg(&client->dev, "write [EMAIL PROTECTED] --> %zd (%ld)\n",
+ count, offset, status, jiffies);
+
+ if (status == count)
+ return count;
+
+ /* REVISIT: at HZ=100, this is sloooow */
+ msleep(1);
+ } while (time_before(write_time, timeout));
+
+ return -ETIMEDOUT;
+}
+
+static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ struct at24_data *at24;
+ ssize_t retval = 0;
+
+ at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
+
+ if (unlikely(!count))
+ return count;
+
+ /*
+ * Write data to chip, protecting against concurrent updates
+ * from this host ... but not from other i2c masters.
+ */
+ mutex_lock(&at24->lock);
+
+ 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;
+ }
+
+ mutex_unlock(&at24->lock);
+
+ return retval;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static int at24_probe(struct i2c_client *client, const struct i2c_device_id
*id)
+{
+ struct at24_platform_data *chip;
+ bool writable;
+ bool use_smbus = false;
+ struct at24_data *at24;
+ int err;
+ unsigned i, num_addresses;
+ kernel_ulong_t magic;
+
+ if (id->driver_data) {
+ chip = kmalloc(sizeof(struct at24_platform_data), GFP_KERNEL);
+ if (!chip) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ magic = id->driver_data;
+ chip->byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
+ magic >>= AT24_SIZE_BYTELEN;
+ chip->page_size = BIT(magic & AT24_BITMASK(AT24_SIZE_PAGESIZE));
+ magic >>= AT24_SIZE_PAGESIZE;
+ chip->flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
+ } else {
+ chip = client->dev.platform_data;
+ if (!chip) {
+ err = -ENODEV;
+ goto err_out;
+ }
+ }
+
+ if (!is_power_of_2(chip->byte_len))
+ dev_warn(&client->dev,
+ "byte_len looks suspicious (no power of 2)!\n");
+ if (!is_power_of_2(chip->page_size))
+ dev_warn(&client->dev,
+ "page_size looks suspicious (no power of 2)!\n");
+
+ /* Use I2C operations unless we're stuck with SMBus extensions. */
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+ if (chip->flags & AT24_FLAG_ADDR16) {
+ err = -EPFNOSUPPORT;
+ goto err_chip;
+ }
+ if (!i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
+ err = -EPFNOSUPPORT;
+ goto err_chip;
+ }
+ use_smbus = true;
+ }
+
+ if (chip->flags & AT24_FLAG_24C00)
+ num_addresses = 8;
+ else
+ num_addresses = (chip->byte_len >>
+ (chip->flags & AT24_FLAG_ADDR16 ? 16 : 8)) + 1;
+
+ at24 = kzalloc(sizeof(struct at24_data) +
+ num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
+ if (!at24) {
+ err = -ENOMEM;
+ goto err_chip;
+ }
+
+ mutex_init(&at24->lock);
+ at24->use_smbus = use_smbus;
+ at24->chip = *chip;
+ at24->num_addresses = num_addresses;
+
+ /*
+ * Export the EEPROM bytes through sysfs, since that's convenient.
+ * By default, only root should see the data (maybe passwords etc)
+ */
+ at24->bin.attr.name = "eeprom";
+ at24->bin.attr.mode = chip->flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
+ at24->bin.attr.owner = THIS_MODULE;
+ at24->bin.read = at24_bin_read;
+ at24->bin.size = chip->byte_len;
+
+ writable = !(chip->flags & AT24_FLAG_READONLY);
+ if (writable) {
+ if (!use_smbus || i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
+
+ unsigned write_max = chip->page_size;
+
+ at24->bin.write = at24_bin_write;
+ at24->bin.attr.mode |= S_IWUSR;
+
+ if (write_max > io_limit)
+ write_max = io_limit;
+ if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
+ write_max = I2C_SMBUS_BLOCK_MAX;
+ at24->write_max = write_max;
+
+ /* buffer (data + address at the beginning) */
+ at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL);
+ if (!at24->writebuf) {
+ err = -ENOMEM;
+ goto err_struct;
+ }
+ } else {
+ dev_warn(&client->dev,
+ "cannot write due to controller restrictions.");
+ }
+ }
+
+ 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%04x unavailable\n",
+ client->addr + i);
+ err = -EADDRINUSE;
+ goto err_clients;
+ }
+ }
+
+ err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
+ if (err)
+ goto err_clients;
+
+ i2c_set_clientdata(client, at24);
+
+ dev_info(&client->dev, "%Zd byte %s EEPROM %s\n",
+ at24->bin.size, client->name,
+ writable ? "(writable)" : "(read-only)");
+ dev_dbg(&client->dev,
+ "page_size %d, num_addresses %d, write_max %d%s\n",
+ chip->page_size, num_addresses,
+ at24->write_max,
+ use_smbus ? ", use_smbus" : "");
+
+ if (id->driver_data)
+ kfree(chip);
+ return 0;
+
+err_clients:
+ for (i = 1; i < num_addresses; i++)
+ if (at24->client[i])
+ i2c_unregister_device(at24->client[i]);
+
+ kfree(at24->writebuf);
+err_struct:
+ kfree(at24);
+err_chip:
+ if (id->driver_data)
+ kfree(chip);
+err_out:
+ dev_dbg(&client->dev, "probe error %d\n", err);
+ return err;
+}
+
+static int __devexit at24_remove(struct i2c_client *client)
+{
+ struct at24_data *at24;
+ int i;
+
+ at24 = i2c_get_clientdata(client);
+ sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
+
+ for (i = 1; i < at24->num_addresses; i++)
+ if (at24->client[i])
+ i2c_unregister_device(at24->client[i]);
+
+ kfree(at24->writebuf);
+ kfree(at24);
+ i2c_set_clientdata(client, NULL);
+ return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static const struct i2c_device_id at24_ids[] = {
+ { "24c00", AT24_DEVICE_MAGIC(AT24_DATA_24C00) },
+ { "24c01", AT24_DEVICE_MAGIC(AT24_DATA_24C01) },
+ { "24c02", AT24_DEVICE_MAGIC(AT24_DATA_24C02) },
+ { "spd", AT24_DEVICE_MAGIC(AT24_DATA_SPD) },
+ { "pcf8570", AT24_DEVICE_MAGIC(AT24_DATA_PCF8570) },
+ { "24c04", AT24_DEVICE_MAGIC(AT24_DATA_24C04) },
+ { "24c08", AT24_DEVICE_MAGIC(AT24_DATA_24C08) },
+ { "24c16", AT24_DEVICE_MAGIC(AT24_DATA_24C16) },
+ { "24c32", AT24_DEVICE_MAGIC(AT24_DATA_24C32) },
+ { "24c64", AT24_DEVICE_MAGIC(AT24_DATA_24C64) },
+ { "24c128", AT24_DEVICE_MAGIC(AT24_DATA_24C128) },
+ { "24c256", AT24_DEVICE_MAGIC(AT24_DATA_24C256) },
+ { "24c512", AT24_DEVICE_MAGIC(AT24_DATA_24C512) },
+ { "24c1024", AT24_DEVICE_MAGIC(AT24_DATA_24C1024) },
+ { "at24", 0 },
+ { /* END OF LIST */ }
+};
+MODULE_DEVICE_TABLE(i2c, at24_ids);
+
+static struct i2c_driver at24_driver = {
+ .driver = {
+ .name = "at24",
+ .owner = THIS_MODULE,
+ },
+ .probe = at24_probe,
+ .remove = __devexit_p(at24_remove),
+ .id_table = at24_ids,
+};
+
+static int __init at24_init(void)
+{
+ io_limit = rounddown_pow_of_two(io_limit);
+ return i2c_add_driver(&at24_driver);
+}
+module_init(at24_init);
+
+static void __exit at24_exit(void)
+{
+ i2c_del_driver(&at24_driver);
+}
+module_exit(at24_exit);
+
+MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
+MODULE_AUTHOR("David Brownell and Wolfram Sang");
+MODULE_LICENSE("GPL");
Index: linux-2.6.26-rc4/include/linux/i2c/at24.h
===================================================================
--- /dev/null
+++ linux-2.6.26-rc4/include/linux/i2c/at24.h
@@ -0,0 +1,104 @@
+#ifndef _LINUX_AT24_H
+#define _LINUX_AT24_H
+
+#include <linux/types.h>
+
+/*
+ * As seen through Linux I2C, differences between the most common types
+ * of I2C memory include:
+ * - How much memory is available (usually specified in bit)?
+ * - What write page size does it support?
+ * - Special flags (16 bit addresses, read_only, world readable)?
+ *
+ * If you set up a custom eeprom type, please make sure you
+ * have double-checked the parameters. Especially page_size needs extra care,
+ * as you risk data loss if your value is bigger than what the chip actually
+ * supports! A typical custom type declaration would look similar to this:
+ *
+ * struct const at24_platform_data my_eeprom_data {
+ * AT24_PLATFORM_DATA(byte_len, page_size, flags);
+ * };
+ *
+ */
+struct at24_platform_data {
+ u32 byte_len; /* size (sum of all addr) */
+ u16 page_size; /* for writes */
+ u8 flags;
+#define AT24_FLAG_ADDR16 0x80
+#define AT24_FLAG_READONLY 0x40
+#define AT24_FLAG_IRUGO 0x20
+#define AT24_FLAG_24C00 0x10
+};
+
+#define AT24_SIZE_BYTELEN 5
+#define AT24_SIZE_PAGESIZE 4
+#define AT24_SIZE_FLAGS 8
+
+#define AT24_BITMASK(x) ((1UL << x) - 1)
+
+/* nest macros to enforce expansion of macros containing parameters */
+#define AT24_PLATFORM_DATA(x) _AT24_PLATFORM_DATA(x)
+
+#define _AT24_PLATFORM_DATA(_len, _page, _flags) \
+ .byte_len = (_len), .page_size = (_page), .flags = (_flags)
+
+/* create non-zero magic value for given eeprom parameters */
+#define AT24_DEVICE_MAGIC(x) _AT24_DEVICE_MAGIC(x)
+
+#define _AT24_DEVICE_MAGIC(_len, _page, _flags) \
+ (((1 << AT24_SIZE_FLAGS | _flags) \
+ << AT24_SIZE_PAGESIZE | ilog2(_page)) \
+ << AT24_SIZE_BYTELEN | ilog2(_len))
+
+/*
+ * Chip data. Parameters are byte_len, page_size and flags
+ */
+
+/* 128 bit chip, I2C A0-A2 ignored */
+#define AT24_DATA_24C00 128 / 8, 1, AT24_FLAG_24C00
+
+/* 1 Kbit chip, some have 16 byte pages: 24lc014, ... */
+#define AT24_DATA_24C01 1024 / 8, 8, 0
+
+/* 2 Kbit chip, some have 16 byte pages: */
+#define AT24_DATA_24C02 2048 / 8, 8, 0
+
+/* 2 Kbit chip, 24c02 in memory DIMMs, some have 16 byte pages */
+#define AT24_DATA_SPD 2048 / 8, 8, AT24_FLAG_READONLY | AT24_FLAG_IRUGO
+
+/* 2 Kbit chip, SRAM, not EEPROM!, no page size issues, write it all at once */
+#define AT24_DATA_PCF8570 2048 / 8, 2048 / 8, 0
+
+/* 4 Kbit chip, I2C A0 is MEM A8 */
+#define AT24_DATA_24C04 4096 / 8, 16, 0
+
+/*
+ * 8 Kbit chip, I2C A1-A0 is MEM A9-A8, works also with 24RF08
+ * (its quirk is handled at i2c-core-level)
+ */
+#define AT24_DATA_24C08 8192 / 8, 16, 0
+
+/* 16 Kbit chip, I2C A2-A0 is MEM A10-A8 */
+#define AT24_DATA_24C16 16384 / 8, 16, 0
+
+/* this second block of EEPROMs uses 16 bit memory addressing */
+
+/* 32 Kbits */
+#define AT24_DATA_24C32 32768 / 8, 32, AT24_FLAG_ADDR16
+
+/* 64 Kbits */
+#define AT24_DATA_24C64 65536 / 8, 32, AT24_FLAG_ADDR16
+
+/* 128 Kbits */
+#define AT24_DATA_24C128 131072 / 8, 64, AT24_FLAG_ADDR16
+
+/* 256 Kbits */
+#define AT24_DATA_24C256 262144 / 8, 64, AT24_FLAG_ADDR16
+
+/* 512 Kbits */
+#define AT24_DATA_24C512 524288 / 8, 128, AT24_FLAG_ADDR16
+
+/* 1 Mbits, I2C A0 is MEM A16 */
+#define AT24_DATA_24C1024 1048576 / 8, 256, AT24_FLAG_ADDR16
+
+#endif /* _LINUX_AT24_H */
--
Dipl.-Ing. Wolfram Sang | http://www.pengutronix.de
Pengutronix - Linux Solutions for Science and Industry
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