i2c: New-style EEPROM driver using 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 <w.sang@pengutronix.de> Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Wolfram Sang
Jean Delvare
parent
e9ca9eb9d7
commit
2b7a5056a0
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@ -14,6 +14,32 @@ config DS1682
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This driver can also be built as a module. If so, the module
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will be called ds1682.
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config AT24
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tristate "EEPROMs from most vendors"
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depends on SYSFS && EXPERIMENTAL
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help
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Enable this driver to get read/write support to most I2C EEPROMs,
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after you configure the driver to know about each EEPROM on
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your target board. Use these generic chip names, instead of
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vendor-specific ones like at24c64 or 24lc02:
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24c00, 24c01, 24c02, spd (readonly 24c02), 24c04, 24c08,
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24c16, 24c32, 24c64, 24c128, 24c256, 24c512, 24c1024
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Unless you like data loss puzzles, always be sure that any chip
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you configure as a 24c32 (32 kbit) or larger is NOT really a
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24c16 (16 kbit) or smaller, and vice versa. Marking the chip
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as read-only won't help recover from this. Also, if your chip
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has any software write-protect mechanism you may want to review the
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code to make sure this driver won't turn it on by accident.
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If you use this with an SMBus adapter instead of an I2C adapter,
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full functionality is not available. Only smaller devices are
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supported (24c16 and below, max 4 kByte).
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This driver can also be built as a module. If so, the module
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will be called at24.
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config SENSORS_EEPROM
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tristate "EEPROM reader"
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depends on EXPERIMENTAL
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@ -10,6 +10,7 @@
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#
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obj-$(CONFIG_DS1682) += ds1682.o
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obj-$(CONFIG_AT24) += at24.o
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obj-$(CONFIG_SENSORS_EEPROM) += eeprom.o
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obj-$(CONFIG_SENSORS_MAX6875) += max6875.o
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obj-$(CONFIG_SENSORS_PCA9539) += pca9539.o
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@ -0,0 +1,583 @@
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/*
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* at24.c - handle most I2C EEPROMs
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*
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* Copyright (C) 2005-2007 David Brownell
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* Copyright (C) 2008 Wolfram Sang, Pengutronix
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/delay.h>
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#include <linux/mutex.h>
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#include <linux/sysfs.h>
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#include <linux/mod_devicetable.h>
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#include <linux/log2.h>
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#include <linux/bitops.h>
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#include <linux/jiffies.h>
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#include <linux/i2c.h>
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#include <linux/i2c/at24.h>
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/*
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* I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
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* Differences between different vendor product lines (like Atmel AT24C or
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* MicroChip 24LC, etc) won't much matter for typical read/write access.
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* There are also I2C RAM chips, likewise interchangeable. One example
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* would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
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*
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* However, misconfiguration can lose data. "Set 16-bit memory address"
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* to a part with 8-bit addressing will overwrite data. Writing with too
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* big a page size also loses data. And it's not safe to assume that the
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* conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
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* uses 0x51, for just one example.
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*
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* Accordingly, explicit board-specific configuration data should be used
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* in almost all cases. (One partial exception is an SMBus used to access
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* "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
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*
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* So this driver uses "new style" I2C driver binding, expecting to be
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* told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
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* similar kernel-resident tables; or, configuration data coming from
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* a bootloader.
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*
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* Other than binding model, current differences from "eeprom" driver are
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* that this one handles write access and isn't restricted to 24c02 devices.
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* It also handles larger devices (32 kbit and up) with two-byte addresses,
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* which won't work on pure SMBus systems.
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*/
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struct at24_data {
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struct at24_platform_data chip;
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bool use_smbus;
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/*
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* Lock protects against activities from other Linux tasks,
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* but not from changes by other I2C masters.
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*/
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struct mutex lock;
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struct bin_attribute bin;
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u8 *writebuf;
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unsigned write_max;
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unsigned num_addresses;
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/*
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* Some chips tie up multiple I2C addresses; dummy devices reserve
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* them for us, and we'll use them with SMBus calls.
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*/
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struct i2c_client *client[];
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};
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/*
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* This parameter is to help this driver avoid blocking other drivers out
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* of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
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* clock, one 256 byte read takes about 1/43 second which is excessive;
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* but the 1/170 second it takes at 400 kHz may be quite reasonable; and
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* at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
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*
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* This value is forced to be a power of two so that writes align on pages.
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*/
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static unsigned io_limit = 128;
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module_param(io_limit, uint, 0);
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MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
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/*
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* Specs often allow 5 msec for a page write, sometimes 20 msec;
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* it's important to recover from write timeouts.
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*/
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static unsigned write_timeout = 25;
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module_param(write_timeout, uint, 0);
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MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
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#define AT24_SIZE_BYTELEN 5
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#define AT24_SIZE_FLAGS 8
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#define AT24_BITMASK(x) (BIT(x) - 1)
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/* create non-zero magic value for given eeprom parameters */
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#define AT24_DEVICE_MAGIC(_len, _flags) \
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((1 << AT24_SIZE_FLAGS | (_flags)) \
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<< AT24_SIZE_BYTELEN | ilog2(_len))
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static const struct i2c_device_id at24_ids[] = {
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/* needs 8 addresses as A0-A2 are ignored */
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{ "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
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/* old variants can't be handled with this generic entry! */
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{ "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
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{ "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
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/* spd is a 24c02 in memory DIMMs */
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{ "spd", AT24_DEVICE_MAGIC(2048 / 8,
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AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
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{ "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
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/* 24rf08 quirk is handled at i2c-core */
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{ "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
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{ "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
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{ "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
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{ "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
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{ "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
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{ "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
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{ "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
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{ "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
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{ "at24", 0 },
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{ /* END OF LIST */ }
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};
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MODULE_DEVICE_TABLE(i2c, at24_ids);
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/*-------------------------------------------------------------------------*/
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/*
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* This routine supports chips which consume multiple I2C addresses. It
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* computes the addressing information to be used for a given r/w request.
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* Assumes that sanity checks for offset happened at sysfs-layer.
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*/
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static struct i2c_client *at24_translate_offset(struct at24_data *at24,
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unsigned *offset)
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{
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unsigned i;
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if (at24->chip.flags & AT24_FLAG_ADDR16) {
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i = *offset >> 16;
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*offset &= 0xffff;
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} else {
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i = *offset >> 8;
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*offset &= 0xff;
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}
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return at24->client[i];
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}
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static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
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unsigned offset, size_t count)
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{
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struct i2c_msg msg[2];
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u8 msgbuf[2];
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struct i2c_client *client;
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int status, i;
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memset(msg, 0, sizeof(msg));
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/*
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* REVISIT some multi-address chips don't rollover page reads to
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* the next slave address, so we may need to truncate the count.
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* Those chips might need another quirk flag.
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*
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* If the real hardware used four adjacent 24c02 chips and that
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* were misconfigured as one 24c08, that would be a similar effect:
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* one "eeprom" file not four, but larger reads would fail when
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* they crossed certain pages.
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*/
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/*
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* Slave address and byte offset derive from the offset. Always
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* set the byte address; on a multi-master board, another master
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* may have changed the chip's "current" address pointer.
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*/
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client = at24_translate_offset(at24, &offset);
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if (count > io_limit)
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count = io_limit;
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/* Smaller eeproms can work given some SMBus extension calls */
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if (at24->use_smbus) {
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if (count > I2C_SMBUS_BLOCK_MAX)
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count = I2C_SMBUS_BLOCK_MAX;
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status = i2c_smbus_read_i2c_block_data(client, offset,
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count, buf);
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dev_dbg(&client->dev, "smbus read %zd@%d --> %d\n",
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count, offset, status);
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return (status < 0) ? -EIO : status;
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}
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/*
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* When we have a better choice than SMBus calls, use a combined
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* I2C message. Write address; then read up to io_limit data bytes.
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* Note that read page rollover helps us here (unlike writes).
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* msgbuf is u8 and will cast to our needs.
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*/
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i = 0;
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if (at24->chip.flags & AT24_FLAG_ADDR16)
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msgbuf[i++] = offset >> 8;
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msgbuf[i++] = offset;
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msg[0].addr = client->addr;
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msg[0].buf = msgbuf;
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msg[0].len = i;
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msg[1].addr = client->addr;
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msg[1].flags = I2C_M_RD;
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msg[1].buf = buf;
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msg[1].len = count;
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status = i2c_transfer(client->adapter, msg, 2);
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dev_dbg(&client->dev, "i2c read %zd@%d --> %d\n",
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count, offset, status);
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if (status == 2)
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return count;
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else if (status >= 0)
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return -EIO;
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else
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return status;
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}
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static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
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char *buf, loff_t off, size_t count)
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{
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struct at24_data *at24;
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ssize_t retval = 0;
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at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
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if (unlikely(!count))
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return count;
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/*
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* Read data from chip, protecting against concurrent updates
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* from this host, but not from other I2C masters.
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*/
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mutex_lock(&at24->lock);
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while (count) {
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ssize_t status;
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status = at24_eeprom_read(at24, buf, off, count);
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if (status <= 0) {
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if (retval == 0)
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retval = status;
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break;
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}
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buf += status;
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off += status;
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count -= status;
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retval += status;
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}
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mutex_unlock(&at24->lock);
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return retval;
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}
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/*
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* REVISIT: export at24_bin{read,write}() to let other kernel code use
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* eeprom data. For example, it might hold a board's Ethernet address, or
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* board-specific calibration data generated on the manufacturing floor.
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*/
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/*
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* Note that if the hardware write-protect pin is pulled high, the whole
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* chip is normally write protected. But there are plenty of product
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* variants here, including OTP fuses and partial chip protect.
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*
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* We only use page mode writes; the alternative is sloooow. This routine
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* writes at most one page.
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*/
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static ssize_t at24_eeprom_write(struct at24_data *at24, char *buf,
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unsigned offset, size_t count)
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{
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struct i2c_client *client;
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struct i2c_msg msg;
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ssize_t status;
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unsigned long timeout, write_time;
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unsigned next_page;
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/* Get corresponding I2C address and adjust offset */
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client = at24_translate_offset(at24, &offset);
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/* write_max is at most a page */
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if (count > at24->write_max)
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count = at24->write_max;
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/* Never roll over backwards, to the start of this page */
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next_page = roundup(offset + 1, at24->chip.page_size);
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if (offset + count > next_page)
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count = next_page - offset;
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/* If we'll use I2C calls for I/O, set up the message */
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if (!at24->use_smbus) {
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int i = 0;
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msg.addr = client->addr;
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msg.flags = 0;
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/* msg.buf is u8 and casts will mask the values */
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msg.buf = at24->writebuf;
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if (at24->chip.flags & AT24_FLAG_ADDR16)
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msg.buf[i++] = offset >> 8;
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msg.buf[i++] = offset;
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memcpy(&msg.buf[i], buf, count);
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msg.len = i + count;
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}
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/*
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* Writes fail if the previous one didn't complete yet. We may
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* loop a few times until this one succeeds, waiting at least
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* long enough for one entire page write to work.
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*/
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timeout = jiffies + msecs_to_jiffies(write_timeout);
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do {
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write_time = jiffies;
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if (at24->use_smbus) {
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status = i2c_smbus_write_i2c_block_data(client,
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offset, count, buf);
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if (status == 0)
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status = count;
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} else {
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status = i2c_transfer(client->adapter, &msg, 1);
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if (status == 1)
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status = count;
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}
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dev_dbg(&client->dev, "write %zd@%d --> %zd (%ld)\n",
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count, offset, status, jiffies);
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if (status == count)
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return count;
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/* REVISIT: at HZ=100, this is sloooow */
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msleep(1);
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} while (time_before(write_time, timeout));
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return -ETIMEDOUT;
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}
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static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
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char *buf, loff_t off, size_t count)
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{
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struct at24_data *at24;
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ssize_t retval = 0;
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at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
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if (unlikely(!count))
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return count;
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/*
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* Write data to chip, protecting against concurrent updates
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* from this host, but not from other I2C masters.
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*/
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mutex_lock(&at24->lock);
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while (count) {
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ssize_t status;
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status = at24_eeprom_write(at24, buf, off, count);
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if (status <= 0) {
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if (retval == 0)
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retval = status;
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break;
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}
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buf += status;
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off += status;
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count -= status;
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retval += status;
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}
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mutex_unlock(&at24->lock);
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return retval;
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}
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/*-------------------------------------------------------------------------*/
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static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
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{
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struct at24_platform_data chip;
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bool writable;
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bool use_smbus = false;
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struct at24_data *at24;
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int err;
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unsigned i, num_addresses;
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kernel_ulong_t magic;
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if (client->dev.platform_data) {
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chip = *(struct at24_platform_data *)client->dev.platform_data;
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} else {
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if (!id->driver_data) {
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err = -ENODEV;
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goto err_out;
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}
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magic = id->driver_data;
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chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
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magic >>= AT24_SIZE_BYTELEN;
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chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
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/*
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* This is slow, but we can't know all eeproms, so we better
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* play safe. Specifying custom eeprom-types via platform_data
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* is recommended anyhow.
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*/
|
||||
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 (!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_out;
|
||||
}
|
||||
if (!i2c_check_functionality(client->adapter,
|
||||
I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
|
||||
err = -EPFNOSUPPORT;
|
||||
goto err_out;
|
||||
}
|
||||
use_smbus = true;
|
||||
}
|
||||
|
||||
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 = kzalloc(sizeof(struct at24_data) +
|
||||
num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
|
||||
if (!at24) {
|
||||
err = -ENOMEM;
|
||||
goto err_out;
|
||||
}
|
||||
|
||||
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%02x 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" : "");
|
||||
|
||||
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_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++)
|
||||
i2c_unregister_device(at24->client[i]);
|
||||
|
||||
kfree(at24->writebuf);
|
||||
kfree(at24);
|
||||
i2c_set_clientdata(client, NULL);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*-------------------------------------------------------------------------*/
|
||||
|
||||
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");
|
||||
|
|
@ -0,0 +1,28 @@
|
|||
#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 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 */
|
||||
Reference in New Issue