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

From: Bartosz Golaszewski
Date: Thu Sep 17 2015 - 10:58:59 EST

2015-09-17 16:55 GMT+02:00 Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>:
> Hi Bartosz,
>
>> On Sep 17, 2015, at 17:42 , Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> wrote:
>>
>> 2015-09-16 18:11 GMT+02:00 Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>:
>>> For DT and in-kernel users there is no interface to the
>>> at24 EEPROMs so provide an NVMEM 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>
>>> ---
>>> drivers/misc/eeprom/at24.c | 219 +++++++++++++++++++++++++++++++++++----------
>>> 1 file changed, 174 insertions(+), 45 deletions(-)
>>>
>>> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
>>> index c6cb7f8..195a45e 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/nvmem-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 nvmem_config *nvmem_config;
>>> + struct nvmem_device *nvmem_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);
>>> +
>>> /*-------------------------------------------------------------------------*/
>>>
>>> /*
>>> @@ -276,17 +286,6 @@ 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
>>> @@ -407,18 +406,10 @@ 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;
>>> -
>>> - 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 */
>>> +
>>> /*
>>> * This lets other kernel code access the eeprom data. For example, it
>>> * might hold a board's Ethernet address, or board-specific calibration
>>> @@ -464,6 +455,91 @@ 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,
>>> +};
>>> +
>>> static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>> {
>>> struct at24_platform_data chip;
>>> @@ -474,6 +550,10 @@ 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_config *regmap_config;
>>> + struct regmap *regmap;
>>> + struct nvmem_config *nvmem_config;
>>> + struct nvmem_device *nvmem_dev;
>>>
>>> if (client->dev.platform_data) {
>>> chip = *(struct at24_platform_data *)client->dev.platform_data;
>>> @@ -541,16 +621,75 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>> }
>>> }
>>>
>>> + regmap_config = devm_kzalloc(&client->dev, sizeof(*regmap_config),
>>> + GFP_KERNEL);
>>> + if (IS_ERR(regmap_config)) {
>>> + err = PTR_ERR(regmap_config);
>>> + dev_err(&client->dev, "%s: regmap_config allocation failed (%d)\n",
>>> + __func__, err);
>>> + return err;
>>> + }
>>> +
>>> + /* use 32 bits as registers, they don't appear on the wire anyway */
>>> + regmap_config->reg_bits = 32;
>>> + regmap_config->val_bits = 8;
>>> + regmap_config->cache_type = REGCACHE_NONE;
>>> + regmap_config->max_register = chip.byte_len;
>>> +
>>> if (chip.flags & AT24_FLAG_TAKE8ADDR)
>>> num_addresses = 8;
>>> else
>>> num_addresses = DIV_ROUND_UP(chip.byte_len,
>>> (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
>>>
>>> + /* we can't use devm_regmap_init_i2c due to the many i2c clients */
>>> + regmap = devm_regmap_init(&client->dev, &regmap_at24_bus,
>>> + client, regmap_config);
>>> + if (IS_ERR(regmap)) {
>>> + err = PTR_ERR(regmap);
>>> + dev_err(&client->dev, "%s: regmap allocation failed (%d)\n",
>>> + __func__, err);
>>> + return err;
>>> + }
>>> +
>>> + nvmem_config = devm_kzalloc(&client->dev, sizeof(*nvmem_config),
>>> + GFP_KERNEL);
>>> + if (IS_ERR(nvmem_config)) {
>>> + err = PTR_ERR(nvmem_config);
>>> + dev_err(&client->dev, "%s: nvmem_config allocation failed (%d)\n",
>>> + __func__, err);
>>> + return err;
>>> + }
>>> + nvmem_config->dev = &client->dev;
>>> + nvmem_config->name = "at24-";
>>> + nvmem_config->id = ida_simple_get(&at24_ida, 0, 0, GFP_KERNEL);
>>> + nvmem_config->owner = THIS_MODULE;
>>> + if (nvmem_config->id < 0) {
>>> + err = nvmem_config->id;
>>> + dev_err(&client->dev, "%s: eeprom id allocation failed (%d)\n",
>>> + __func__, err);
>>> + return err;
>>> + }
>>> +
>>> + nvmem_dev = nvmem_register(nvmem_config);
>>> + if (IS_ERR(nvmem_dev)) {
>>> + err = PTR_ERR(nvmem_dev);
>>> + dev_err(&client->dev, "%s: nvmem_register failed (%d)\n",
>>> + __func__, err);
>>> + goto err_out;
>>> + }
>>> +
>>> at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
>>> num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
>>> - if (!at24)
>>> - return -ENOMEM;
>>> + if (!at24) {
>>> + err = -ENOMEM;
>>> + goto err_out;
>>> + }
>>> +
>>> + at24->regmap = regmap;
>>> + at24->regmap_config = regmap_config;
>>> + at24->nvmem_config = nvmem_config;
>>> + at24->nvmem_dev = nvmem_dev;
>>>
>>> mutex_init(&at24->lock);
>>> at24->use_smbus = use_smbus;
>>> @@ -558,16 +697,6 @@ 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;
>>
>> Hi Pantelis,
>>
>> this breaks the ABI.
>>
>> Additionally: the nvmem file is 0 in size with this patch and reading
>> it produces the following NULL pointer dereference on BeagleBone
>> Black:
>>
>> I'm using an at24cs02 chip, that works with mainline.
>>
>> [ 147.023405] Unable to handle kernel NULL pointer dereference at
>> virtual address 00000002
>> [ 147.041713] pgd = de6f8000
>> [ 147.053787] [00000002] *pgd=9e6eb831, *pte=00000000, *ppte=00000000
>> [ 147.070152] Internal error: Oops: 17 [#1] SMP ARM
>> [ 147.084543] Modules linked in: gpio_pca953x ina2xx ipv6 omap_rng
>> rng_core rtc_omap omap_wdt at24 cpufreq_dt leds_gpio thermal_sys
>> led_class hwmon
>> [ 147.109168] CPU: 0 PID: 177 Comm: dd Not tainted 4.3.0-rc1-acme+ #18
>> [ 147.126126] Hardware name: Generic AM33XX (Flattened Device Tree)
>> [ 147.142765] task: de68c380 ti: de672000 task.ti: de672000
>> [ 147.158659] PC is at at24_read+0x1c4/0x200 [at24]
>> [ 147.173739] LR is at at24_read+0x54/0x200 [at24]
>> [ 147.188538] pc : [<bf02a20c>] lr : [<bf02a09c>] psr: 60080013
>> [ 147.188538] sp : de673d88 ip : bf02b17c fp : ffffc440
>> [ 147.220290] r10: de673da4 r9 : c09c6100 r8 : de6f3300
>> [ 147.235487] r7 : de77c1d0 r6 : 00000000 r5 : 00000000 r4 : 00000001
>> [ 147.251957] r3 : 00000001 r2 : de673dc0 r1 : de673dc0 r0 : 00000001
>> [ 147.268442] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
>> [ 147.285639] Control: 10c5387d Table: 9e6f8019 DAC: 00000051
>> [ 147.301332] Process dd (pid: 177, stack limit = 0xde672218)
>> [ 147.316864] Stack: (0xde673d88 to 0xde674000)
>> [ 147.331094] 3d80: 00000080 00000080 00000100
>> 00000000 00000100 de77c1f0
>> [ 147.349553] 3da0: 00000001 00000000 00000000 00000000 00000000
>> 00000000 00000000 00000100
>> [ 147.368085] 3dc0: de68c380 00000101 00000101 de6c2e00 c0a7f4ac
>> c0a7f4e4 00000101 00000000
>> [ 147.386542] 3de0: de6f3200 bf02a290 00000001 c06b5d3c de617800
>> c04707a8 00000101 00000020
>> [ 147.404852] 3e00: 00000000 00000000 60080013 c0a7d784 00000000
>> c0093c74 00000001 de617800
>> [ 147.423274] 3e20: 00000000 00000001 00000101 de6f3200 00000101
>> 00000101 00000000 c04709c0
>> [ 147.441694] 3e40: 00000001 c0093c74 00000001 00000101 00000000
>> 00000000 00000000 00000000
>> [ 147.460163] 3e60: 00000000 dba5a94c 00000000 c05a15ac c0a6e5dc
>> de641980 00000000 de6f3200
>> [ 147.478710] 3e80: 00000000 c01f0fb8 00000000 00000000 00000200
>> c008da64 dba5a940 de673f80
>> [ 147.497227] 3ea0: 00000200 00000000 00000000 dba5a94c 00000000
>> c01f08ac 00000000 00000000
>> [ 147.515693] 3ec0: 00000256 000af008 de673f04 de641980 c06d16bc
>> 00000200 000af008 de673f80
>> [ 147.534153] 3ee0: 00000000 00000000 00000000 c0176af8 de641988
>> ddcf1868 de641980 00000000
>> [ 147.552575] 3f00: 00000000 00000000 00000000 c0326588 00000000
>> 00000000 00000001 de641980
>> [ 147.570949] 3f20: 00000200 00000000 00000000 c0176c04 60080013
>> de6afc00 de641980 00000200
>> [ 147.589215] 3f40: 000af008 de673f80 00000000 00000000 00000000
>> c0177acc de6afc00 de6afe80
>> [ 147.607452] 3f60: de641980 de641980 de641980 00000200 000af008
>> 00000000 00000000 c0177c00
>> [ 147.625712] 3f80: 00000000 00000000 000aea10 000aea10 00000000
>> 000af008 00000003 c000ff44
>> [ 147.643928] 3fa0: de672000 c000fda0 000aea10 00000000 00000000
>> 000af008 00000200 00000000
>> [ 147.662047] 3fc0: 000aea10 00000000 000af008 00000003 000af008
>> 00000000 000af008 00000000
>> [ 147.680078] 3fe0: 00000000 beec7aac 0000fc00 b6f2c07c 60080010
>> 00000000 00000000 00000000
>> [ 147.698148] [<bf02a20c>] (at24_read [at24]) from [<bf02a290>]
>> (regmap_at24_read+0x48/0x78 [at24])
>> [ 147.717080] [<bf02a290>] (regmap_at24_read [at24]) from
>> [<c04707a8>] (_regmap_raw_read+0xdc/0x1f4)
>> [ 147.736127] [<c04707a8>] (_regmap_raw_read) from [<c04709c0>]
>> (regmap_raw_read+0x100/0x160)
>> [ 147.754515] [<c04709c0>] (regmap_raw_read) from [<c05a15ac>]
>> (bin_attr_nvmem_read+0x54/0x8c)
>> [ 147.773017] [<c05a15ac>] (bin_attr_nvmem_read) from [<c01f0fb8>]
>> (sysfs_kf_bin_read+0xa0/0xac)
>> [ 147.791728] [<c01f0fb8>] (sysfs_kf_bin_read) from [<c01f08ac>]
>> (kernfs_fop_read+0xb8/0x180)
>> [ 147.810159] [<c01f08ac>] (kernfs_fop_read) from [<c0176af8>]
>> (__vfs_read+0x2c/0xe0)
>> [ 147.827787] [<c0176af8>] (__vfs_read) from [<c0177acc>] (vfs_read+0x90/0xf0)
>> [ 147.844732] [<c0177acc>] (vfs_read) from [<c0177c00>] (SyS_read+0x44/0x88)
>> [ 147.861535] [<c0177c00>] (SyS_read) from [<c000fda0>]
>> (ret_fast_syscall+0x0/0x1c)
>> [ 147.878728] Code: e28d1038 e0812002 a3a03001 e5425004 (e1d620b2)
>> [ 147.894527] ---[ end trace 4f2f3a675fee7446 ]---
>>
>> Best regards,
>> Bartosz Golaszewski
>>
>>> at24->macc.read = at24_macc_read;
>>>
>>> writable = !(chip.flags & AT24_FLAG_READONLY);
>>> @@ -578,9 +707,6 @@ 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)
>>> @@ -590,8 +716,10 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>> /* buffer (data + address at the beginning) */
>>> at24->writebuf = devm_kzalloc(&client->dev,
>>> write_max + 2, GFP_KERNEL);
>>> - if (!at24->writebuf)
>>> - return -ENOMEM;
>>> + if (!at24->writebuf) {
>>> + err = -ENOMEM;
>>> + goto err_out;
>>> + }
>>> } else {
>>> dev_warn(&client->dev,
>>> "cannot write due to controller restrictions.");
>>> @@ -612,14 +740,10 @@ 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)
>>> - 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,
>>> + at24->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) {
>>> @@ -635,10 +759,14 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>> return 0;
>>>
>>> err_clients:
>>> +
>>> for (i = 1; i < num_addresses; i++)
>>> if (at24->client[i])
>>> i2c_unregister_device(at24->client[i]);
>>>
>>> +err_out:
>>> + ida_simple_remove(&at24_ida, nvmem_config->id);
>>> +
>>> return err;
>>> }
>>>
>>> @@ -648,11 +776,12 @@ static int at24_remove(struct i2c_client *client)
>>> int i;
>>>
>>> at24 = i2c_get_clientdata(client);
>>> - sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
>>>
>>> for (i = 1; i < at24->num_addresses; i++)
>>> i2c_unregister_device(at24->client[i]);
>>>
>>> + nvmem_unregister(at24->nvmem_dev);
>>> +
>>> return 0;
>>> }
>>>
>>>
>>> 1.7.12
>
> Thanks for the bug report. Are you using the user-space API to read from the device?

Yes, we have a working setup where the device is instantiated via
/sys/class/i2c-adapter/.../new_device and the data is read from the
'eeprom' attribute. Given the wide adoption of the at24 series I don't
think we'll ever be able to remove this file - even after moving to
nvmem.

Best regards,
Bartosz Golaszewski
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