From: "Krzysztof Wilczyński" <kw@linux.com>
To: Maximilian Luz <luzmaximilian@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PCI: Add sysfs attribute for PCI device power state
Date: Sun, 15 Nov 2020 07:08:25 +0100 [thread overview]
Message-ID: <X7DF2ZyVnyIFjdC1@rocinante> (raw)
In-Reply-To: <20201102141520.831630-1-luzmaximilian@gmail.com>
Hi Maximilian,
On 20-11-02 15:15:20, Maximilian Luz wrote:
> While most PCI power-states can be queried from user-space via lspci,
> this has some limits. Specifically, lspci fails to provide an accurate
> value when the device is in D3cold as it has to resume the device before
> it can access its power state via the configuration space, leading to it
> reporting D0 or another on-state. Thus lspci can, for example, not be
> used to diagnose power-consumption issues for devices that can enter
> D3cold or to ensure that devices properly enter D3cold at all.
>
> To alleviate this issue, introduce a new sysfs device attribute for the
> PCI power state, showing the current power state as seen by the kernel.
Very nice! Thank you for adding this.
[...]
> +/* PCI power state */
> +static ssize_t power_state_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct pci_dev *pci_dev = to_pci_dev(dev);
> + pci_power_t state = READ_ONCE(pci_dev->current_state);
> +
> + return sprintf(buf, "%s\n", pci_power_name(state));
> +}
> +static DEVICE_ATTR_RO(power_state);
[...]
Curious, why did you decide to use the READ_ONCE() macro here? Some
other drivers exposing data through sysfs use, but certainly not all.
Krzysztof
next prev parent reply other threads:[~2020-11-15 6:08 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-02 14:15 [PATCH] PCI: Add sysfs attribute for PCI device power state Maximilian Luz
2020-11-15 6:08 ` Krzysztof Wilczyński [this message]
2020-11-15 12:45 ` Maximilian Luz
2020-11-15 20:27 ` Bjorn Helgaas
2020-11-15 21:19 ` Maximilian Luz
2020-11-18 17:49 ` Bjorn Helgaas
2020-11-18 23:28 ` Maximilian Luz
2020-11-18 19:19 ` Bjorn Helgaas
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