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Date:	Thu, 18 Feb 2016 11:22:07 +0100
From:	Bartosz Golaszewski <bgolaszewski@...libre.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	GregKH <greg@...ah.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Wolfram Sang <wsa@...-dreams.de>, broonie@...nel.org,
	vz@...ia.com, LKML <linux-kernel@...r.kernel.org>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Subject: Re: [PATCHv5 3/7] eeprom: at24: extend driver to plug into the NVMEM framework

2016-02-17 21:07 GMT+01:00 Andrew Lunn <andrew@...n.ch>:
> Add a regmap for accessing the EEPROM, and then use that with the
> NVMEM framework. Set the NVMEM config structure to enable backward, so
> that the 'eeprom' file in sys is provided by the framework.
>
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> Acked-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/misc/eeprom/Kconfig |   2 +
>  drivers/misc/eeprom/at24.c  | 121 +++++++++++++++++++++++++++++---------------
>  2 files changed, 82 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/misc/eeprom/Kconfig b/drivers/misc/eeprom/Kconfig
> index 04f2e1fa9dd1..24935473393b 100644
> --- a/drivers/misc/eeprom/Kconfig
> +++ b/drivers/misc/eeprom/Kconfig
> @@ -3,6 +3,8 @@ menu "EEPROM support"
>  config EEPROM_AT24
>         tristate "I2C EEPROMs / RAMs / ROMs from most vendors"
>         depends on I2C && SYSFS
> +       select REGMAP
> +       select NVMEM
>         help
>           Enable this driver to get read/write support to most I2C EEPROMs
>           and compatible devices like FRAMs, SRAMs, ROMs etc. After you
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 5d7c0900fa1b..f15cda93fc4c 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -15,7 +15,6 @@
>  #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/bitops.h>
> @@ -23,6 +22,8 @@
>  #include <linux/of.h>
>  #include <linux/acpi.h>
>  #include <linux/i2c.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/regmap.h>
>  #include <linux/platform_data/at24.h>
>
>  /*
> @@ -64,12 +65,15 @@ struct at24_data {
>          * but not from changes by other I2C masters.
>          */
>         struct mutex lock;
> -       struct bin_attribute bin;
>
>         u8 *writebuf;
>         unsigned write_max;
>         unsigned num_addresses;
>
> +       struct regmap_config regmap_config;
> +       struct nvmem_config nvmem_config;
> +       struct nvmem_device *nvmem;
> +
>         /*
>          * Some chips tie up multiple I2C addresses; dummy devices reserve
>          * them for us, and we'll use them with SMBus calls.
> @@ -283,17 +287,6 @@ static ssize_t at24_read(struct at24_data *at24,
>         return retval;
>  }
>
> -static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
> -               struct bin_attribute *attr,
> -               char *buf, loff_t off, size_t count)
> -{
> -       struct at24_data *at24;
> -
> -       at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> -       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
> @@ -414,16 +407,6 @@ static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
>         return retval;
>  }
>
> -static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
> -               struct bin_attribute *attr,
> -               char *buf, loff_t off, size_t count)
> -{
> -       struct at24_data *at24;
> -
> -       at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> -       return at24_write(at24, buf, off, count);
> -}
> -
>  /*-------------------------------------------------------------------------*/
>
>  /*
> @@ -450,6 +433,49 @@ static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
>
>  /*-------------------------------------------------------------------------*/
>
> +/*
> + * Provide a regmap interface, which is registered with the NVMEM
> + * framework
> +*/
> +static int at24_regmap_read(void *context, const void *reg, size_t reg_size,
> +                           void *val, size_t val_size)
> +{
> +       struct at24_data *at24 = context;
> +       off_t offset = *(u32 *)reg;
> +       int err;
> +
> +       err = at24_read(at24, val, offset, val_size);
> +       if (err)
> +               return err;
> +       return 0;
> +}
> +
> +static int at24_regmap_write(void *context, const void *data, size_t count)
> +{
> +       struct at24_data *at24 = context;
> +       const char *buf;
> +       u32 offset;
> +       size_t len;
> +       int err;
> +
> +       memcpy(&offset, data, sizeof(offset));
> +       buf = (const char *)data + sizeof(offset);
> +       len = count - sizeof(offset);
> +
> +       err = at24_write(at24, buf, offset, len);
> +       if (err)
> +               return err;
> +       return 0;
> +}
> +
> +static const struct regmap_bus at24_regmap_bus = {
> +       .read = at24_regmap_read,
> +       .write = at24_regmap_write,
> +       .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
> +};
> +
> +/*-------------------------------------------------------------------------*/
> +
>  #ifdef CONFIG_OF
>  static void at24_get_ofdata(struct i2c_client *client,
>                 struct at24_platform_data *chip)
> @@ -481,6 +507,7 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>         struct at24_data *at24;
>         int err;
>         unsigned i, num_addresses;
> +       struct regmap *regmap;
>
>         if (client->dev.platform_data) {
>                 chip = *(struct at24_platform_data *)client->dev.platform_data;
> @@ -573,16 +600,6 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>         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)
> -        */
> -       sysfs_bin_attr_init(&at24->bin);
> -       at24->bin.attr.name = "eeprom";
> -       at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
> -       at24->bin.read = at24_bin_read;
> -       at24->bin.size = chip.byte_len;
> -
>         at24->macc.read = at24_macc_read;
>
>         writable = !(chip.flags & AT24_FLAG_READONLY);
> @@ -593,9 +610,6 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>
>                         at24->macc.write = at24_macc_write;
>
> -                       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)
> @@ -627,14 +641,38 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>                 }
>         }
>
> -       err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
> -       if (err)
> +       at24->regmap_config.reg_bits = 32;
> +       at24->regmap_config.val_bits = 8;
> +       at24->regmap_config.reg_stride = 1;
> +       at24->regmap_config.max_register = chip.byte_len - 1;
> +
> +       regmap = devm_regmap_init(&client->dev, &at24_regmap_bus, at24,
> +                                 &at24->regmap_config);
> +       if (IS_ERR(regmap)) {
> +               dev_err(&client->dev, "regmap init failed\n");
> +               err = PTR_ERR(regmap);
>                 goto err_clients;
> +       }
> +
> +       at24->nvmem_config.name = dev_name(&client->dev);
> +       at24->nvmem_config.dev = &client->dev;
> +       at24->nvmem_config.read_only = !writable;
> +       at24->nvmem_config.root_only = true;
> +       at24->nvmem_config.owner = THIS_MODULE;
> +       at24->nvmem_config.compat = true;
> +       at24->nvmem_config.base_dev = &client->dev;
> +
> +       at24->nvmem = nvmem_register(&at24->nvmem_config);
> +
> +       if (IS_ERR(at24->nvmem)) {
> +               err = PTR_ERR(at24->nvmem);
> +               goto err_clients;
> +       }
>
>         i2c_set_clientdata(client, at24);
>
> -       dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
> -               at24->bin.size, client->name,
> +       dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
> +               chip.byte_len, client->name,
>                 writable ? "writable" : "read-only", at24->write_max);
>         if (use_smbus == I2C_SMBUS_WORD_DATA ||
>             use_smbus == I2C_SMBUS_BYTE_DATA) {
> @@ -663,7 +701,8 @@ static int at24_remove(struct i2c_client *client)
>         int i;
>
>         at24 = i2c_get_clientdata(client);
> -       sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
> +
> +       nvmem_unregister(at24->nvmem);
>
>         for (i = 1; i < at24->num_addresses; i++)
>                 i2c_unregister_device(at24->client[i]);
> --
> 2.7.0
>

Tested-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

Best regards,
Bartosz Golaszewski

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