linux-kernel - Re: [PATCH v4 2/8] usb: misc: onboard_dev: add support for non-hub devices

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Date: Tue, 27 Feb 2024 17:55:07 +0000
From: Matthias Kaehlcke <mka@...omium.org>
To: Javier Carrasco <javier.carrasco@...fvision.net>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Helen Koike <helen.koike@...labora.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Russell King <linux@...linux.org.uk>,
	linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 2/8] usb: misc: onboard_dev: add support for non-hub
 devices

On Thu, Feb 22, 2024 at 03:42:26PM +0100, Javier Carrasco wrote:
> On 21.02.24 20:24, Matthias Kaehlcke wrote:
> > On Tue, Feb 20, 2024 at 03:05:46PM +0100, Javier Carrasco wrote:
> >> Most of the functionality this driver provides can be used by non-hub
> >> devices as well.
> >>
> >> To account for the hub-specific code, add a flag to the device data
> >> structure and check its value for hub-specific code.
> > 
> > Please mention that the driver doesn't power off non-hub devices
> > during system suspend.
> > 
> >> Signed-off-by: Javier Carrasco <javier.carrasco@...fvision.net>
> >> ---
> >>  drivers/usb/misc/onboard_usb_dev.c |  3 ++-
> >>  drivers/usb/misc/onboard_usb_dev.h | 10 ++++++++++
> >>  2 files changed, 12 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/usb/misc/onboard_usb_dev.c b/drivers/usb/misc/onboard_usb_dev.c
> >> index 2103af2cb2a6..f43130a6786f 100644
> >> --- a/drivers/usb/misc/onboard_usb_dev.c
> >> +++ b/drivers/usb/misc/onboard_usb_dev.c
> >> @@ -129,7 +129,8 @@ static int __maybe_unused onboard_dev_suspend(struct device *dev)
> >>  		if (!device_may_wakeup(node->udev->bus->controller))
> >>  			continue;
> >>  
> >> -		if (usb_wakeup_enabled_descendants(node->udev)) {
> >> +		if (usb_wakeup_enabled_descendants(node->udev) ||
> >> +		    !onboard_dev->pdata->is_hub) {
> > 
> > 
> > This check isn't dependent on characteristics of the USB devices processed
> > in this loop, therefore it can be performed at function entry. Please combine
> > it with the check of 'always_powered_in_suspend'. It's also an option to
> > omit the check completely, 'always_powered_in_suspend' will never be set for
> > non-hub devices (assuming the sysfs attribute isn't added).
> > 
> 
> The attribute will not be available for non-hub devices in v5. However,
> if the check is completely removed, will power_off not stay true at the
> end of the function, always leading to a device power off? As you said,
> 'always_powered_in_suspend' will not be set for non-hub devices.

Even without the sysfs attribute the field 'always_powered_in_suspend' could
be set to true by probe() for non-hub devices.