linux-kernel - Re: [PATCH 1/2] usb: core: Centralize device state update logic

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Message-ID: <24db7c90-16d6-4122-8bda-aee2a2c930bf@rowland.harvard.edu>
Date: Mon, 13 Oct 2025 09:16:28 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Kuen-Han Tsai <khtsai@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] usb: core: Centralize device state update logic

On Mon, Oct 13, 2025 at 10:01:22AM +0800, Kuen-Han Tsai wrote:
> Introduce a new static inline function, update_usb_device_state(), to
> centralize the process of changing a device's state, including the
> management of active_duration during suspend/resume transitions.
> 
> This change prepares for adding tracepoints, allowing tracing logic to
> be added in a single, central location within the new helper function.
> 
> Signed-off-by: Kuen-Han Tsai <khtsai@...gle.com>
> ---
>  drivers/usb/core/hub.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 256fe8c86828d51c33442345acdb7f3fe80a98ce..ce3d94c960470e9be7979b1021551eab5fd03517 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2147,6 +2147,20 @@ static void update_port_device_state(struct usb_device *udev)
>  	}
>  }
>  
> +static inline void update_usb_device_state(struct usb_device *udev,
> +					   enum usb_device_state new_state)
> +{
> +	if (udev->state == USB_STATE_SUSPENDED &&
> +	    new_state != USB_STATE_SUSPENDED)
> +		udev->active_duration -= jiffies;
> +	else if (new_state == USB_STATE_SUSPENDED &&
> +		 udev->state != USB_STATE_SUSPENDED)
> +		udev->active_duration += jiffies;
> +
> +	udev->state = new_state;
> +	update_port_device_state(udev);
> +}

This seems complicated enough to be a standalone function, not inline.

Alan Stern