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

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Date:   Tue, 16 Apr 2019 12:34:54 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Gaurav Kohli <gkohli@...eaurora.org>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        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 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 ;-)

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