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

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Message-ID: <20191028080858.GB1718@redsun51.ssa.fujisawa.hgst.com>
Date:   Mon, 28 Oct 2019 17:08:58 +0900
From:   Keith Busch <kbusch@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Chris Healy <Chris.Healy@....aero>, Jens Axboe <axboe@...com>,
        Sagi Grimberg <sagi@...mberg.me>, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org,
        Akinobu Mita <akinobu.mita@...il.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH] nvme: Add hardware monitoring support

On Mon, Oct 28, 2019 at 08:39:53AM +0100, Christoph Hellwig wrote:
> On Sun, Oct 27, 2019 at 07:41:56PM -0700, Guenter Roeck wrote:
> > nvme devices report temperature information in the controller information
> > (for limits) and in the smart log. Currently, the only means to retrieve
> > this information is the nvme command line interface, which requires
> > super-user privileges.
> > 
> > At the same time, it would be desirable to use NVME temperature information
> > for thermal control.
> > 
> > This patch adds support to read NVME temperatures from the kernel using the
> > hwmon API and adds temperature zones for NVME drives. The thermal subsystem
> > can use this information to set thermal policies, and userspace can access
> > it using libsensors and/or the "sensors" command.
> 
> So these reported values seem to generate some interest.  Adding Akinobu
> Mita who also planned to wire them up to the thermal framework.  I don't
> really know either upper layer so I'm not sure which is the right one,
> but with this just like with the previous series I am quite worried that
> we add a lot of kernel boilerplate code for information people can
> trivially get using nvme-cli.

I think it's nvme-cli requires root, where this conveniently doesn't
need those elevated rights.

I'm not familiar with either upper level framework either; my only review
comment for this patch is to use devm_kfree() for the error cases.