linux-kernel - Re: [PATCH RFC] eeprom: at24: extend driver to plug into the NVMEM framework

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Date:	Mon, 17 Aug 2015 10:48:54 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Andrew Lunn <andrew@...n.ch>, wsa@...-dreams.de
CC:	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH RFC] eeprom: at24: extend driver to plug into the NVMEM
 framework

Hi Andrew,

Thanks for the patch, few comments other than Stefan's comments.

On 16/08/15 03:54, Andrew Lunn wrote:
> Add a read only regmap for accessing the EEPROM, and then use that
> with the NVMEM framework.
>
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
>   drivers/misc/eeprom/at24.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 65 insertions(+)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 2d3db81be099..0e80c0c09d4e 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -22,6 +22,8 @@
>   #include <linux/jiffies.h>
>   #include <linux/of.h>
>   #include <linux/i2c.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/regmap.h>
>   #include <linux/platform_data/at24.h>
>
>   /*
> @@ -69,6 +71,10 @@ struct at24_data {
>   	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.
> @@ -471,6 +477,34 @@ 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;
> +
> +	return at24_read(at24, val, offset, val_size);
> +}
> +
> +static int at24_regmap_write(void *context, const void *data, size_t count)
> +{
> +	struct at24_data *at24 = context;
> +
> +	return at24_write(at24, data, 0, count);
> +}
> +
> +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)
> @@ -502,6 +536,7 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>   	int err;
>   	unsigned i, num_addresses;
>   	kernel_ulong_t magic;
> +	struct regmap *regmap;
>
>   	if (client->dev.platform_data) {
>   		chip = *(struct at24_platform_data *)client->dev.platform_data;
> @@ -644,6 +679,30 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>   	if (err)
>   		goto err_clients;
>
> +	at24->regmap_config.reg_bits = 32;
> +	at24->regmap_config.val_bits = 8;
> +	at24->regmap_config.reg_stride = 1;
> +	at24->regmap_config.max_register = at24->bin.size - 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_sysfs;
> +	}
> +
> +	at24->nvmem_config.name = dev_name(&client->dev);
> +	at24->nvmem_config.dev = &client->dev;
> +	at24->nvmem_config.read_only = !writable;
> +	at24->nvmem_config.owner = THIS_MODULE;
> +
> +	at24->nvmem = nvmem_register(&at24->nvmem_config);
> +	if (IS_ERR(at24->nvmem)) {
> +		err = PTR_ERR(at24->nvmem);
> +		goto err_sysfs;
> +	}
> +
>   	i2c_set_clientdata(client, at24);
>
>   	dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
> @@ -662,6 +721,9 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>
>   	return 0;
>
> +err_sysfs:
> +	sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
> +

?? Not sure Why this code is still needed. Can't we remove it?

Is this the the same binary file which is exposed by nvmem in 
/sys/bus/nvmem too?

--srini
>   err_clients:
>   	for (i = 1; i < num_addresses; i++)
>   		if (at24->client[i])
> @@ -676,6 +738,9 @@ static int at24_remove(struct i2c_client *client)
>   	int i;
>
>   	at24 = i2c_get_clientdata(client);
> +
> +	nvmem_unregister(at24->nvmem);
> +
>   	sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
>
>   	for (i = 1; i < at24->num_addresses; i++)
>
--
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