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Subject: Re: [PATCH v2] nvmem: core: Set no-read-write provider to avoid
 userspace read/write
From:   Gaurav Kohli <gkohli@codeaurora.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        linux-kernel@vger.kernel.org
Cc:     linux-arm-msm@vger.kernel.org
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Date:   Mon, 25 Mar 2019 11:45:13 +0530
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On 3/22/2019 11:42 PM, Gaurav Kohli wrote:
> Hi Srinivas,
>
> Thanks for the patch, Something like this only i have tested in the 
> morning, instead of unused, i have put dev group inside config as well.
>
> We will test the exact patch and update the same.
>
> Regards
>
> Gaurav
>
> On 3/22/2019 8:32 PM, Srinivas Kandagatla wrote:
>>
>>
>> On 20/03/2019 17:50, Gaurav Kohli wrote:
>>>
>>>> Is root only option not helping you in this case?
>>> Yes we want to protect at root level as well, i mean it is better if 
>>> we can avoid exposing to userspace at all.
>> Can you try below patch!
>>
Hi Srinivas,

Thanks for the patch.

I have checked the patch and also tested the same , and it is working as 
expected(no creation of nvmem sysfs)

Applied with some conflict on line 41.

Reviewed-by: Gaurav Kohli <gkohli@codeaurora.org>
Tested-by: Gaurav Kohli <gkohli@codeaurora.org>

Regards

Gaurav


>>>>
>>>> We could go down the route of adding new config option something 
>>>> like CONFIG_NVMEM_NO_SYSFS_ENTRY to prevent adding nvmem entry in 
>>>> userspace.
>>>>
>>>> Let me know if you are happy to create a patch for this change?
>>>
>>> I am happy with either way config option or dt binding(seems easy), 
>>> please let me know we will post new patch for the same.
>> DT way is totally NAK.
>>
>>
>> --------------------------->cut<-----------------------------------
>>
>> From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> Date: Wed, 20 Mar 2019 16:15:21 +0000
>> Subject: [PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY
>>
>> Some users might not want to expose nvmem entry to sysfs and
>> only intend to use kernel interface so add such provision.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>>  Documentation/ABI/stable/sysfs-bus-nvmem |  2 ++
>>  drivers/nvmem/Kconfig                    |  5 +++++
>>  drivers/nvmem/core.c                     | 11 ++++++-----
>>  3 files changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem 
>> b/Documentation/ABI/stable/sysfs-bus-nvmem
>> index 5923ab4620c5..12aab0a85fea 100644
>> --- a/Documentation/ABI/stable/sysfs-bus-nvmem
>> +++ b/Documentation/ABI/stable/sysfs-bus-nvmem
>> @@ -6,6 +6,8 @@ Description:
>>          This file allows user to read/write the raw NVMEM contents.
>>          Permissions for write to this file depends on the nvmem
>>          provider configuration.
>> +        Note: This file is not present if CONFIG_NVMEM_NO_SYSFS_ENTRY
>> +        is enabled
>>
>>          ex:
>>          hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
>> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
>> index 0a7a470ee859..6ab3276d287c 100644
>> --- a/drivers/nvmem/Kconfig
>> +++ b/drivers/nvmem/Kconfig
>> @@ -192,4 +192,9 @@ config SC27XX_EFUSE
>>        This driver can also be built as a module. If so, the module
>>        will be called nvmem-sc27xx-efuse.
>>
>> +config NVMEM_NO_SYSFS_ENTRY
>> +    bool "No nvmem sysfs entry"
>> +
>> +    help
>> +        Say Yes if you do not want to add nvmem entry to sysfs.
>>  endif
>> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
>> index b9a0270883a0..c70f183fe379 100644
>> --- a/drivers/nvmem/core.c
>> +++ b/drivers/nvmem/core.c
>> @@ -216,7 +216,7 @@ static const struct attribute_group 
>> nvmem_bin_rw_group = {
>>      .attrs        = nvmem_attrs,
>>  };
>>
>> -static const struct attribute_group *nvmem_rw_dev_groups[] = {
>> +static const __maybe_unused struct attribute_group 
>> *nvmem_rw_dev_groups[] = {
>>      &nvmem_bin_rw_group,
>>      NULL,
>>  };
>> @@ -240,7 +240,7 @@ static const struct attribute_group 
>> nvmem_bin_ro_group = {
>>      .attrs        = nvmem_attrs,
>>  };
>>
>> -static const struct attribute_group *nvmem_ro_dev_groups[] = {
>> +static const __maybe_unused struct attribute_group 
>> *nvmem_ro_dev_groups[] = {
>>      &nvmem_bin_ro_group,
>>      NULL,
>>  };
>> @@ -265,7 +265,7 @@ static const struct attribute_group 
>> nvmem_bin_rw_root_group = {
>>      .attrs        = nvmem_attrs,
>>  };
>>
>> -static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
>> +static const __maybe_unused struct attribute_group 
>> *nvmem_rw_root_dev_groups[] = {
>>      &nvmem_bin_rw_root_group,
>>      NULL,
>>  };
>> @@ -289,7 +289,7 @@ static const struct attribute_group 
>> nvmem_bin_ro_root_group = {
>>      .attrs        = nvmem_attrs,
>>  };
>>
>> -static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
>> +static const __maybe_unused struct attribute_group 
>> *nvmem_ro_root_dev_groups[] = {
>>      &nvmem_bin_ro_root_group,
>>      NULL,
>>  };
>> @@ -688,6 +688,7 @@ struct nvmem_device *nvmem_register(const struct 
>> nvmem_config *config)
>>      nvmem->read_only = device_property_present(config->dev, 
>> "read-only") |
>>                 config->read_only;
>>
>> +#if !defined(CONFIG_NVMEM_NO_SYSFS_ENTRY)
>>      if (config->root_only)
>>          nvmem->dev.groups = nvmem->read_only ?
>>              nvmem_ro_root_dev_groups :
>> @@ -696,7 +697,7 @@ struct nvmem_device *nvmem_register(const struct 
>> nvmem_config *config)
>>          nvmem->dev.groups = nvmem->read_only ?
>>              nvmem_ro_dev_groups :
>>              nvmem_rw_dev_groups;
>> -
>> +#endif
>>      device_initialize(&nvmem->dev);
>>
>>      dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", 
>> config->name);
>
-- 
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