Re: [PATCH] i2c: eeprom: at24: Provide an EEPROM framework interface

[Pantelis Antoniou]

Hi Maxime,

> On May 15, 2015, at 17:19 , Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> 
> On Thu, May 14, 2015 at 09:06:23AM +0300, Pantelis Antoniou wrote:
>> 
>>> On May 13, 2015, at 23:36 , Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
>>> 
>>> Hi Pantelis,
>>> 
>>> On Wed, May 13, 2015 at 10:38:17AM +0300, Pantelis Antoniou wrote:
>>>> For DT and in-kernel users there is no interface to the
>>>> at24 EEPROMs so provide an EEPROM framework interface.
>>>> 
>>>> This allows us to use AT24 based EEPROMs and reference them
>>>> from within the DT tree.
>>>> 
>>>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
>>> 
>>> You should probably mention that the EEPROM framework hasn't been
>>> merged yet.
>>> 
>> 
>> Well, thatâs true. But itâs on version 4 and it does do what I need it
>> to do, namely provide a DT interface for in-kernel users.
> 
> I was just meaning that people not aware of the fact that the
> framework was not merged might apply it, and that would result in an
> instant breakage, that's all.
> 
> It's actually pretty nice that you convert this driver over to the
> EEPROM framework.
> 

Thanks. Itâs really broadly used and the framework works fine.


>> 
>>>> ---
>>>> drivers/misc/eeprom/at24.c | 222 +++++++++++++++++++++++++++++++++++----------
>>>> 1 file changed, 174 insertions(+), 48 deletions(-)
>>>> 
>>>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
>>>> index 2d3db81..afa719a 100644
>>>> --- a/drivers/misc/eeprom/at24.c
>>>> +++ b/drivers/misc/eeprom/at24.c
>>>> @@ -3,6 +3,7 @@
>>>> *
>>>> * Copyright (C) 2005-2007 David Brownell
>>>> * Copyright (C) 2008 Wolfram Sang, Pengutronix
>>>> + * Copyright (C) 2015 Pantelis Antoniou, Konsulko Group
>>>> *
>>>> * This program is free software; you can redistribute it and/or modify
>>>> * it under the terms of the GNU General Public License as published by
>>>> @@ -23,6 +24,9 @@
>>>> #include <linux/of.h>
>>>> #include <linux/i2c.h>
>>>> #include <linux/platform_data/at24.h>
>>>> +#include <linux/regmap.h>
>>>> +#include <linux/eeprom-provider.h>
>>>> +#include <linux/io.h>
>>>> 
>>>> /*
>>>> * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
>>>> @@ -63,12 +67,16 @@ 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 regmap *regmap;
>>>> +	struct eeprom_config *eeprom_config;
>>>> +	struct eeprom_device *eeprom_dev;
>>>> +
>>>> 	/*
>>>> 	 * Some chips tie up multiple I2C addresses; dummy devices reserve
>>>> 	 * them for us, and we'll use them with SMBus calls.
>>>> @@ -131,6 +139,8 @@ static const struct i2c_device_id at24_ids[] = {
>>>> };
>>>> MODULE_DEVICE_TABLE(i2c, at24_ids);
>>>> 
>>>> +static DEFINE_IDA(at24_ida);
>>>> +
>>>> /*-------------------------------------------------------------------------*/
>>>> 
>>>> /*
>>>> @@ -301,17 +311,6 @@ 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
>>>> @@ -432,21 +431,10 @@ 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;
>>>> -
>>>> -	if (unlikely(off >= attr->size))
>>>> -		return -EFBIG;
>>>> -
>>>> -	at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
>>>> -	return at24_write(at24, buf, off, count);
>>>> -}
>>>> -
>>>> /*-------------------------------------------------------------------------*/
>>>> 
>>>> +/* panto: using the EEPROM framework macc is superfluous */
>>>> +
>>> 
>>> Is it? it was kind of one of the point to be able to remove the memory
>>> accessors stuff (which is only used by that driver btw).
>> 
>> Yes it completely redundant now. But itâs not my call to remove it, that would
>> be Wolfram.
> 
> There's still a user of that stuff though, some davinci board iirc,
> that would need to port that user to the EEPROM framework too.
> 
>>>> /*
>>>> * This lets other kernel code access the eeprom data. For example, it
>>>> * might hold a board's Ethernet address, or board-specific calibration
>>>> @@ -492,6 +480,91 @@ static void at24_get_ofdata(struct i2c_client *client,
>>>> { }
>>>> #endif /* CONFIG_OF */
>>>> 
>>>> +static int regmap_at24_read(void *context,
>>>> +			    const void *reg, size_t reg_size,
>>>> +			    void *val, size_t val_size)
>>>> +{
>>>> +	struct i2c_client *client = context;
>>>> +	struct at24_data *at24;
>>>> +	unsigned int offset;
>>>> +	int ret;
>>>> +
>>>> +	/* reg bits is hardcoded to 32 bits */
>>>> +	BUG_ON(reg_size != 4);
>>>> +	offset = __raw_readl(reg);
>>>> +
>>>> +	at24 = i2c_get_clientdata(client);
>>>> +	if (at24 == NULL)
>>>> +		return -ENODEV;
>>>> +
>>>> +	/* val bytes is always 1 */
>>>> +	BUG_ON(at24->regmap_config->val_bits != 8);
>>>> +
>>>> +	ret = at24_read(at24, val, offset, val_size);
>>>> +	if (ret < 0)
>>>> +		return ret;
>>>> +	if (ret != val_size)
>>>> +		return -EINVAL;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int regmap_at24_gather_write(void *context,
>>>> +				    const void *reg, size_t reg_size,
>>>> +				    const void *val, size_t val_size)
>>>> +{
>>>> +	struct i2c_client *client = context;
>>>> +	struct at24_data *at24;
>>>> +	unsigned int offset;
>>>> +	int ret;
>>>> +
>>>> +	at24 = i2c_get_clientdata(client);
>>>> +	if (at24 == NULL)
>>>> +		return -ENODEV;
>>>> +
>>>> +	BUG_ON(reg_size != 4);
>>>> +	offset = __raw_readl(reg);
>>>> +
>>>> +	/* val bytes is always 1 */
>>>> +	BUG_ON(at24->regmap_config->val_bits != 8);
>>>> +
>>>> +	ret = at24_write(at24, val, offset, val_size);
>>>> +	if (ret < 0)
>>>> +		return ret;
>>>> +	if (ret != val_size)
>>>> +		return -EINVAL;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int regmap_at24_write(void *context, const void *data, size_t count)
>>>> +{
>>>> +	struct i2c_client *client = context;
>>>> +	struct at24_data *at24;
>>>> +	unsigned int reg_bytes, offset;
>>>> +
>>>> +	at24 = i2c_get_clientdata(client);
>>>> +	if (at24 == NULL)
>>>> +		return -ENODEV;
>>>> +
>>>> +	reg_bytes = at24->regmap_config->reg_bits / 8;
>>>> +	offset = reg_bytes;
>>>> +
>>>> +	BUG_ON(reg_bytes != 4);
>>>> +	BUG_ON(count <= offset);
>>>> +
>>>> +	return regmap_at24_gather_write(context, data, reg_bytes,
>>>> +			data + offset, count - offset);
>>>> +}
>>>> +
>>>> +static struct regmap_bus regmap_at24_bus = {
>>>> +	.read = regmap_at24_read,
>>>> +	.write = regmap_at24_write,
>>>> +	.gather_write = regmap_at24_gather_write,
>>>> +	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
>>>> +	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
>>> 
>>> I wouldn't expect the content of the EEPROM to change of endianness
>>> when we change the kernelâs
>> 
>> It doesnât matter really; these EEPROMs are byte accessible, and the register
>> values are completely internal to the driver.
> 
> Ah, right. My bad :)
> 

No worries :)

> Maxime
> 
> -- 
> Maxime Ripard, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com

Regards

â Pantelis

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