linux-kernel - Re: [PATCH] nvmem: core: add NVMEM

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Message-ID: <66c3794b-ee84-f746-e686-e5477b78e981@linaro.org>
Date:   Tue, 16 Apr 2019 10:44:01 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Gaurav Kohli <gkohli@...eaurora.org>
Cc:     gregkh@...uxfoundation.org, maxime.ripard@...tlin.com,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmem: core: add NVMEM_SYSFS Kconfig



On 16/04/2019 10:34, Mika Westerberg wrote:
> On Tue, Apr 16, 2019 at 10:49:22AM +0530, Gaurav Kohli wrote:
>> Hi Srinivas,
>>
>> Thanks for the patch,
>> By default NVMEM_SYSFS should be set true, those whose don't want they can
>> disable the same.
>>
>> If we go with disable option, there are chances of eeprom may break in below
>> case:
>>
>> if (config->compat) {
>>                  rval = nvmem_sysfs_setup_compat(nvmem, config); -> this will
>> return error as config is disabled.
>>                  if (rval)
>>                          goto err_device_del;
>>          }
> 
> I also think this may cause problems with Thunderbolt devices because
> the upgradeable NVM is exposed to the userspace via these sysfs files
> and those are being used by fwupd. If the files disappear it makes NVM
> upgrade somewhat harder ;-)
Thanks Mika and Kohli for input.

As Kohli suggested we could make NVMEM_SYSFS default to y so that the 
sysfs file is available by default like before and user/board specific 
can decide to deselect it.

Let me know if thats Okay with you, I can spin that in v2.

--srini

> 
> At least it would be good to include following as part of this series if
> you plan to disable the sysfs entries by default:
> 
> diff --git a/drivers/thunderbolt/Kconfig b/drivers/thunderbolt/Kconfig
> index f4869c38c7e4..dd5facab0af2 100644
> --- a/drivers/thunderbolt/Kconfig
> +++ b/drivers/thunderbolt/Kconfig
> @@ -7,6 +7,7 @@ menuconfig THUNDERBOLT
>   	select CRYPTO
>   	select CRYPTO_HASH
>   	select NVMEM
> +	select NVMEM_SYSFS
>   	help
>   	  Thunderbolt Controller driver. This driver is required if you
>   	  want to hotplug Thunderbolt devices on Apple hardware or on PCs
>