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

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Message-ID: <174ce57a-3197-4251-831f-205ec5cfeae9@wolfvision.net>
Date: Thu, 22 Feb 2024 15:42:26 +0100
From: Javier Carrasco <javier.carrasco@...fvision.net>
To: Matthias Kaehlcke <mka@...omium.org>
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 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.

>>  			power_off = false;
>>  			break;
>>  		}
> 
> Without code context: please omit the creation of the 'always_powered_in_suspend'
> attribute for non-hub devices. As per above we don't plan to hone it, so it
> shouldn't exist.

Best regards,
Javier Carrasco