Re: [PATCH 3/7] eeprom: at24: extend driver to plug into the NVMEM framework

[Bartosz Golaszewski <bgolaszewski@baylibre.com>]

2016-01-28 16:42 GMT+01:00 Andrew Lunn <andrew@lunn.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@lunn.ch>
> ---
>  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
>

Hi Andrew,

the patch works, but I'm hitting the following BUG when instantiating
an at24c32 device:

# echo 24c32 0x54 > /sys/class/i2c-adapter/i2c-2/new_device
[    3.741893] BUG: key de753e8c not in .data!
[    3.749166] ------------[ cut here ]------------
[    3.756649] WARNING: CPU: 0 PID: 102 at
kernel/locking/lockdep.c:3002 __kernfs_create_file+0x60/0xc4()
[    3.769048] DEBUG_LOCKS_WARN_ON(1)
[    3.772463] Modules linked in: at24(+) nvmem_core cpufreq_dt
omap_wdt thermal_sys leds_gpio led_class hwmon
[    3.788301] CPU: 0 PID: 102 Comm: udevd Not tainted 4.5.0-rc1-acme+ #7
[    3.797833] Hardware name: Generic AM33XX (Flattened Device Tree)
[    3.806920] [<c0017d44>] (unwind_backtrace) from [<c0014034>]
(show_stack+0x10/0x14)
[    3.817762] [<c0014034>] (show_stack) from [<c036b478>]
(dump_stack+0x84/0x9c)
[    3.828071] [<c036b478>] (dump_stack) from [<c003c850>]
(warn_slowpath_common+0x7c/0xb8)
[    3.839284] [<c003c850>] (warn_slowpath_common) from [<c003c8bc>]
(warn_slowpath_fmt+0x30/0x40)
[    3.851154] [<c003c8bc>] (warn_slowpath_fmt) from [<c01fbf3c>]
(__kernfs_create_file+0x60/0xc4)
[    3.863025] [<c01fbf3c>] (__kernfs_create_file) from [<c01fc794>]
(sysfs_add_file_mode_ns+0x98/0x1bc)
[    3.875488] [<c01fc794>] (sysfs_add_file_mode_ns) from [<c01fca40>]
(sysfs_create_bin_file+0x38/0x44)
[    3.888000] [<c01fca40>] (sysfs_create_bin_file) from [<bf033770>]
(nvmem_register+0x2cc/0x34c [nvmem_core])
[    3.901190] [<bf033770>] (nvmem_register [nvmem_core]) from
[<bf03c958>] (at24_probe+0x430/0x59c [at24])
[    3.914055] [<bf03c958>] (at24_probe [at24]) from [<c054be80>]
(i2c_device_probe+0x168/0x1fc)
[    3.925926] [<c054be80>] (i2c_device_probe) from [<c045ba44>]
(driver_probe_device+0x208/0x2c0)
[    3.938003] [<c045ba44>] (driver_probe_device) from [<c045bb90>]
(__driver_attach+0x94/0x98)
[    3.949821] [<c045bb90>] (__driver_attach) from [<c0459d80>]
(bus_for_each_dev+0x6c/0xa0)
[    3.961373] [<c0459d80>] (bus_for_each_dev) from [<c045b038>]
(bus_add_driver+0x18c/0x214)
[    3.973037] [<c045b038>] (bus_add_driver) from [<c045c4f4>]
(driver_register+0x78/0xf8)
[    3.984458] [<c045c4f4>] (driver_register) from [<c054ca00>]
(i2c_register_driver+0x2c/0x80)
[    3.996349] [<c054ca00>] (i2c_register_driver) from [<c0009804>]
(do_one_initcall+0x80/0x1e0)
[    4.008344] [<c0009804>] (do_one_initcall) from [<c0123110>]
(do_init_module+0x5c/0x1d4)
[    4.019910] [<c0123110>] (do_init_module) from [<c00cb2e4>]
(load_module+0x1cc0/0x1f48)
[    4.031378] [<c00cb2e4>] (load_module) from [<c00cb71c>]
(SyS_finit_module+0x64/0x74)
[    4.042665] [<c00cb71c>] (SyS_finit_module) from [<c000f820>]
(ret_fast_syscall+0x0/0x1c)
[    4.054322] ---[ end trace 692db3ff57b96549 ]---
[    4.062228] at24 2-0054: 4096 byte 24c32 EEPROM, writable, 1 bytes/write
[    4.073224] i2c i2c-2: new_device: Instantiated device 24c32 at 0x54

It seems to result in the nvmem attribute having 0 size while the
legacy eeprom file has size corresponding with the chip's memory area
size in bytes.

Best regards,
Bartosz Golaszewski