linux-kernel - Re: [PATCH] usb: hub: Clear Port Reset Change during init/resume

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Date:	Wed, 16 Oct 2013 01:32:06 +0400
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Julius Werner <jwerner@...omium.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Benson Leung <bleung@...omium.org>,
	Vincent Palatin <vpalatin@...omium.org>,
	Duncan Laurie <dlaurie@...omium.org>
Subject: Re: [PATCH] usb: hub: Clear Port Reset Change during init/resume

Hello.

On 10/16/2013 01:23 AM, Julius Werner wrote:

> This patch adds the Port Reset Change flag to the set of bits that are
> preemptively cleared on init/resume of a hub. In theory this bit should
> never be set unexpectedly... in practice it can still happen if BIOS,
> SMM or ACPI code plays around with USB devices without cleaning up
> correctly. This is especially dangerous for XHCI root hubs, which don't
> generate any more Port Status Change Events until all change bits are
> cleared, so this is a good precaution to have (similar to how it's
> already done for the Warm Port Reset Change flag).

> Signed-off-by: Julius Werner <jwerner@...omium.org>
> ---
>   drivers/usb/core/hub.c | 5 +++++
>   1 file changed, 5 insertions(+)

> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index e6b682c..c9ef5b8 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1130,6 +1130,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>   			usb_clear_port_feature(hub->hdev, port1,
>   					USB_PORT_FEAT_C_ENABLE);
>   		}
> +		if ((portchange & USB_PORT_STAT_C_RESET)) {

    Hm, why these double parens?

WBR, Sergei

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