eeprom: at24: support reading the serial number for 24csxx

The chips from the at24cs family have two memory areas - a regular
read-write block and a read-only area containing the serial number.

The latter is visible on a different slave address (the address of the
rw memory block + 0x08). In order to access both blocks the user needs
to instantiate a regular at24c device for the rw block address and a
corresponding at24cs device on the serial number block address.

Add a function that allows to access the serial number and assign it
to at24->read_func if the chip allows serial number read operations
and the driver was passed the relevant flag for this device.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 6acf35a..3b27ff1 100644 (file)
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -134,16 +134,34 @@ static const struct i2c_device_id at24_ids[] = {
        { "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) },
+       { "24cs01",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
        { "24c02",      AT24_DEVICE_MAGIC(2048 / 8,     0) },
+       { "24cs02",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
        /* 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) },
+       { "24cs04",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
        /* 24rf08 quirk is handled at i2c-core */
        { "24c08",      AT24_DEVICE_MAGIC(8192 / 8,     0) },
+       { "24cs08",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
        { "24c16",      AT24_DEVICE_MAGIC(16384 / 8,    0) },
+       { "24cs16",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
        { "24c32",      AT24_DEVICE_MAGIC(32768 / 8,    AT24_FLAG_ADDR16) },
+       { "24cs32",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_ADDR16 |
+                               AT24_FLAG_SERIAL |
+                               AT24_FLAG_READONLY) },
        { "24c64",      AT24_DEVICE_MAGIC(65536 / 8,    AT24_FLAG_ADDR16) },
+       { "24cs64",     AT24_DEVICE_MAGIC(16,
+                               AT24_FLAG_ADDR16 |
+                               AT24_FLAG_SERIAL |
+                               AT24_FLAG_READONLY) },
        { "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) },
@@ -276,6 +294,59 @@ static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
        return -ETIMEDOUT;
 }
 
+static ssize_t at24_eeprom_read_serial(struct at24_data *at24, char *buf,
+                                      unsigned int offset, size_t count)
+{
+       unsigned long timeout, read_time;
+       struct i2c_client *client;
+       struct i2c_msg msg[2];
+       u8 addrbuf[2];
+       int status;
+
+       client = at24_translate_offset(at24, &offset);
+
+       memset(msg, 0, sizeof(msg));
+       msg[0].addr = client->addr;
+       msg[0].buf = addrbuf;
+
+       /*
+        * The address pointer of the device is shared between the regular
+        * EEPROM array and the serial number block. The dummy write (part of
+        * the sequential read protocol) ensures the address pointer is reset
+        * to the desired position.
+        */
+       if (at24->chip.flags & AT24_FLAG_ADDR16) {
+               /*
+                * For 16 bit address pointers, the word address must contain
+                * a '10' sequence in bits 11 and 10 regardless of the
+                * intended position of the address pointer.
+                */
+               addrbuf[0] = 0x08;
+               addrbuf[1] = offset;
+               msg[0].len = 2;
+       } else {
+               /*
+                * Otherwise the word address must begin with a '10' sequence,
+                * regardless of the intended address.
+                */
+               addrbuf[0] = 0x80 + offset;
+               msg[0].len = 1;
+       }
+
+       msg[1].addr = client->addr;
+       msg[1].flags = I2C_M_RD;
+       msg[1].buf = buf;
+       msg[1].len = count;
+
+       loop_until_timeout(timeout, read_time) {
+               status = i2c_transfer(client->adapter, msg, 2);
+               if (status == 2)
+                       return count;
+       }
+
+       return -ETIMEDOUT;
+}
+
 /*
  * Note that if the hardware write-protect pin is pulled high, the whole
  * chip is normally write protected. But there are plenty of product
@@ -577,8 +648,13 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
        at24->chip = chip;
        at24->num_addresses = num_addresses;
 
-       at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
-                                         : at24_eeprom_read_i2c;
+       if (chip.flags & AT24_FLAG_SERIAL) {
+               at24->read_func = at24_eeprom_read_serial;
+       } else {
+               at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
+                                                 : at24_eeprom_read_i2c;
+       }
+
        if (at24->use_smbus) {
                if (at24->use_smbus_write == I2C_SMBUS_I2C_BLOCK_DATA)
                        at24->write_func = at24_eeprom_write_smbus_block;

diff --git a/include/linux/platform_data/at24.h b/include/linux/platform_data/at24.h
index fcfdfe3..d595874 100644 (file)
--- a/include/linux/platform_data/at24.h
+++ b/include/linux/platform_data/at24.h
@@ -48,6 +48,7 @@ struct at24_platform_data {
 #define AT24_FLAG_READONLY     BIT(6)  /* sysfs-entry will be read-only */
 #define AT24_FLAG_IRUGO                BIT(5)  /* sysfs-entry will be world-readable */
 #define AT24_FLAG_TAKE8ADDR    BIT(4)  /* take always 8 addresses (24c00) */
+#define AT24_FLAG_SERIAL       BIT(3)  /* factory-programmed serial number */
 
        void            (*setup)(struct nvmem_device *nvmem, void *context);
        void            *context;