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Date:   Wed, 15 May 2019 13:15:19 -0600
From:   Keith Busch <keith.busch@intel.com>
To:     Akinobu Mita <akinobu.mita@gmail.com>
Cc:     linux-nvme@lists.infradead.org, linux-pm@vger.kernel.org,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH 1/2] nvme: add thermal zone infrastructure
Message-ID: <20190515191518.GA21916@localhost.localdomain>
References: <1557933437-4693-1-git-send-email-akinobu.mita@gmail.com>
 <1557933437-4693-2-git-send-email-akinobu.mita@gmail.com>
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On Thu, May 16, 2019 at 12:17:16AM +0900, Akinobu Mita wrote:
> +int nvme_thermal_zones_register(struct nvme_ctrl *ctrl)
> +{
> +	struct nvme_smart_log *log;
> +	int ret;
> +	int i;
> +
> +	log = kzalloc(sizeof(*log), GFP_KERNEL);
> +	if (!log)
> +		return -ENOMEM;
> +
> +	ret = nvme_get_log(ctrl, NVME_NSID_ALL, NVME_LOG_SMART, 0,
> +			   log, sizeof(*log), 0);
> +	if (ret) {
> +		ret = ret > 0 ? -EINVAL : ret;
> +		goto free_log;
> +	}
> +
> +	for (i = 0; i < ARRAY_SIZE(ctrl->tzdev); i++) {
> +		struct thermal_zone_device *tzdev;
> +
> +		if (i && !le16_to_cpu(log->temp_sensor[i - 1]))
> +			continue;
> +		if (ctrl->tzdev[i])
> +			continue;
> +
> +		tzdev = nvme_thermal_zone_register(ctrl, i);
> +		if (!IS_ERR(tzdev))
> +			ctrl->tzdev[i] = tzdev;
> +	}
> +
> +free_log:
> +	kfree(log);
> +
> +	return ret;
> +}

Since this routine is intended for use in the device initialization path,
the error returns are extra important. We have used < 0 to indicate we
need to abandon initialization because we won't be able communicate with
the device if we proceed. Since thermal reporting is not mandatory to
manage our controllers, out-of-memory or a device that doesn't support
SMART should just return 0. We should only halt init if the controller
is unresponsive here.

In general, I'm okay with this feature.