target/linux/generic-2.6/patches-2.6.27/450-i2c_at24_add_kernel_interface_read_write.patch

   1 Subject: [PATCH 2/3] I2C: at24: add kernel interface for reading/writing EEPROM
   2 Date: Monday 25 August 2008
   3 From: Kevin Hilman <khilman@deeprootsystems.com>
   4 To: davinci-linux-open-source@linux.davincidsp.com
   5
   6 This patch adds an interface by which other kernel code can read/write
   7 detected EEPROM.
   8
   9 The platform code registers a 'setup' callback with the
  10 at24_platform_data.  When the at24 driver detects an EEPROM, it fills
  11 out the read and write functions of at24_iface and calls the setup
  12 callback.  The platform code can then use the read/write functions in
  13 the at24_iface struct for reading and writing the EEPROM.
  14
  15 Original idea, review and updates by David Brownell <david-b@pacbell.net>
  16
  17 Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
  18 ---
  19  drivers/i2c/chips/at24.c |   42 +++++++++++++++++++++++++++++++++++-------
  20  include/linux/i2c/at24.h |   10 ++++++++++
  21  2 files changed, 45 insertions(+), 7 deletions(-)
  22
  23 --- a/drivers/i2c/chips/at24.c
  24 +++ b/drivers/i2c/chips/at24.c
  25 @@ -53,6 +53,7 @@
  26
  27  struct at24_data {
  28         struct at24_platform_data chip;
  29 +       struct at24_iface iface;
  30         bool use_smbus;
  31
  32         /*
  33 @@ -264,13 +265,6 @@ static ssize_t at24_bin_read(struct kobj
  34
  35
  36  /*
  37 - * REVISIT: export at24_bin{read,write}() to let other kernel code use
  38 - * eeprom data. For example, it might hold a board's Ethernet address, or
  39 - * board-specific calibration data generated on the manufacturing floor.
  40 - */
  41 -
  42 -
  43 -/*
  44   * Note that if the hardware write-protect pin is pulled high, the whole
  45   * chip is normally write protected. But there are plenty of product
  46   * variants here, including OTP fuses and partial chip protect.
  47 @@ -386,6 +380,30 @@ static ssize_t at24_bin_write(struct kob
  48
  49  /*-------------------------------------------------------------------------*/
  50
  51 +/*
  52 + * This lets other kernel code access the eeprom data. For example, it
  53 + * might hold a board's Ethernet address, or board-specific calibration
  54 + * data generated on the manufacturing floor.
  55 + */
  56 +
  57 +static ssize_t at24_iface_read(struct at24_iface *iface, char *buf,
  58 +                             off_t offset, size_t count)
  59 +{
  60 +       struct at24_data *at24 = container_of(iface, struct at24_data, iface);
  61 +
  62 +       return at24_eeprom_read(at24, buf, offset, count);
  63 +}
  64 +
  65 +static ssize_t at24_iface_write(struct at24_iface *iface, char *buf,
  66 +                              off_t offset, size_t count)
  67 +{
  68 +       struct at24_data *at24 = container_of(iface, struct at24_data, iface);
  69 +
  70 +       return at24_eeprom_write(at24, buf, offset, count);
  71 +}
  72 +
  73 +/*-------------------------------------------------------------------------*/
  74 +
  75  static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
  76  {
  77         struct at24_platform_data chip;
  78 @@ -413,6 +431,9 @@ static int at24_probe(struct i2c_client
  79                  * is recommended anyhow.
  80                  */
  81                 chip.page_size = 1;
  82 +
  83 +               chip.setup = NULL;
  84 +               chip.context = NULL;
  85         }
  86
  87         if (!is_power_of_2(chip.byte_len))
  88 @@ -449,6 +470,9 @@ static int at24_probe(struct i2c_client
  89                 goto err_out;
  90         }
  91
  92 +       at24->iface.read = at24_iface_read;
  93 +       at24->iface.write = at24_iface_write;
  94 +
  95         mutex_init(&at24->lock);
  96         at24->use_smbus = use_smbus;
  97         at24->chip = chip;
  98 @@ -521,6 +545,10 @@ static int at24_probe(struct i2c_client
  99                 at24->write_max,
 100                 use_smbus ? ", use_smbus" : "");
 101
 102 +       /* export data to kernel code */
 103 +       if (chip.setup)
 104 +               chip.setup(&at24->iface, chip.context);
 105 +
 106         return 0;
 107
 108  err_clients:
 109 --- a/include/linux/i2c/at24.h
 110 +++ b/include/linux/i2c/at24.h
 111 @@ -15,6 +15,13 @@
 112   * is bigger than what the chip actually supports!
 113   */
 114
 115 +struct at24_iface {
 116 +       ssize_t (*read)(struct at24_iface *, char *buf, off_t offset,
 117 +                       size_t count);
 118 +       ssize_t (*write)(struct at24_iface *, char *buf, off_t offset,
 119 +                        size_t count);
 120 +};
 121 +
 122  struct at24_platform_data {
 123         u32             byte_len;               /* size (sum of all addr) */
 124         u16             page_size;              /* for writes */
 125 @@ -23,6 +30,9 @@ struct at24_platform_data {
 126  #define AT24_FLAG_READONLY     0x40    /* sysfs-entry will be read-only */
 127  #define AT24_FLAG_IRUGO                0x20    /* sysfs-entry will be world-readable */
 128  #define AT24_FLAG_TAKE8ADDR    0x10    /* take always 8 addresses (24c00) */
 129 +
 130 +       int             (*setup)(struct at24_iface *, void *context);
 131 +       void            *context;
 132  };
 133
 134  #endif /* _LINUX_AT24_H */