Re: [PATCHv4 3/7] eeprom: at24: extend driver to plug into the NVMEM framework

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 16/02/16 23:41, Andrew Lunn wrote:
> 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>

This patch looks good to me, Please feel free to add my Ack.

> ---
>   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]);
>