linux-kernel - Re: [PATCH v2] nvme: Add hardware monitoring support

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Message-ID: <20191031134642.GC4763@lst.de>
Date:   Thu, 31 Oct 2019 14:46:42 +0100
From:   Christoph Hellwig <hch@....de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Christoph Hellwig <hch@....de>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Sagi Grimberg <sagi@...mberg.me>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-nvme@...ts.infradead.org,
        Linux PM <linux-pm@...r.kernel.org>,
        Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH v2] nvme: Add hardware monitoring support

On Wed, Oct 30, 2019 at 07:54:47PM -0700, Guenter Roeck wrote:
> On 10/30/19 7:05 AM, Christoph Hellwig wrote:
>> On Wed, Oct 30, 2019 at 08:16:48PM +0900, Akinobu Mita wrote:
>>> The nvme_init_identify() can be called multiple time in nvme ctrl's
>>> lifetime (e.g 'nvme reset /dev/nvme*' or suspend/resume paths), so
>>> should we need to prevent nvme_hwmon_init() from registering hwmon
>>> device more than twice?
>>>
>>> In the nvme thermal zone patchset[1], thernal zone is registered in
>>> nvme_init_identify and unregistered in nvme_stop_ctrl().
>>
>> So Guenter said above the thermal subsystem could use the information
>> from hwmon as well.  Does this mean this patch would solve your needs
>> as well?
>>
> Depends on the requirements. Unlike hwmon/iio, we don't have clear
> guidelines describing when thermal vs. hwmon would be a better choice.
> There is some interconnect between thermal and hwmon, but quite often
> it is a one-way street (hwmon devices can easily register thermal
> zones, for thermal zone devices it is a bit more difficult to register
> associated hwmon devices).

I'd like to hear from Akinobu-san if this also solves the thermal zone
use case.  If so I'd be much happier as we at least solve two use cases
with one patch.