linux-kernel - Re: [PATCH v3] nvme: Add hardware monitoring support

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Date:   Sat, 2 Nov 2019 01:19:03 +0900
From:   Akinobu Mita <akinobu.mita@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Keith Busch <kbusch@...nel.org>, Chris Healy <cphealy@...il.com>,
        Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-nvme@...ts.infradead.org, Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3] nvme: Add hardware monitoring support

2019年11月1日(金) 12:56 Guenter Roeck <linux@...ck-us.net>:
> +void nvme_hwmon_init(struct nvme_ctrl *ctrl)
> +{
> +       struct device *dev = ctrl->device;

Should we use 'ctrl->dev' instead of 'ctrl->device'?

The 'ctrl->device' is a pointer to char device and the '->of_node' member
is NULL.

So if devm_hwmon_device_register_with_info() (i.e. __hwmon_device_register)
is called with 'ctrl->device', it doesn't attempt to register a sensor to a
DT thermal zone (i.e. hwmon_thermal_add_sensor() is not called at all).

This change was required, when I tried this nvme hwmon patch with the
following DT thermal setup.

https://lore.kernel.org/linux-devicetree/1561990354-4084-3-git-send-email-akinobu.mita@gmail.com/

> +       struct nvme_hwmon_data *data;
> +       struct device *hwmon;
> +       int err;
> +
> +       data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return;
> +
> +       data->ctrl = ctrl;
> +       mutex_init(&data->read_lock);
> +
> +       err = nvme_hwmon_get_smart_log(data);
> +       if (err) {
> +               dev_warn(dev, "Failed to read smart log (error %d)\n", err);
> +               devm_kfree(dev, data);
> +               return;
> +       }
> +
> +       hwmon = devm_hwmon_device_register_with_info(dev, dev_name(dev), data,
> +                                                    &nvme_hwmon_chip_info,
> +                                                    NULL);

If the above change is applied, the second 'name' argument is changed
from 'nvme0' to '0000:01:00.0' as a side effect.  So we may want to
change the second argument, too.

> +       if (IS_ERR(hwmon)) {
> +               dev_warn(dev, "Failed to instantiate hwmon device\n");
> +               devm_kfree(dev, data);
> +       }
> +}