From mboxrd@z Thu Jan  1 00:00:00 1970
Authentication-Results: mx.groups.io;
 dkim=missing; spf=pass (domain: redhat.com, ip: 209.132.183.28, mailfrom: lersek@redhat.com)
Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28])
 by groups.io with SMTP; Wed, 31 Jul 2019 04:37:23 -0700
Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11])
	(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by mx1.redhat.com (Postfix) with ESMTPS id 7AE2B3082120;
	Wed, 31 Jul 2019 11:37:22 +0000 (UTC)
Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-110.ams2.redhat.com [10.36.116.110])
	by smtp.corp.redhat.com (Postfix) with ESMTP id 82E65600CC;
	Wed, 31 Jul 2019 11:37:20 +0000 (UTC)
Subject: Re: [PATCH] MdeModulePkg/UsbBusDxe: Return error when the device is not present
To: Marcin Wojtas <mw@semihalf.com>, devel@edk2.groups.io
Cc: leif.lindholm@linaro.org, ard.biesheuvel@linaro.org, jsd@semihalf.com,
 jaz@semihalf.com, feng.tian@intel.com, michael.d.kinney@intel.com,
 liming.gao@intel.com
References: <1564554319-26810-1-git-send-email-mw@semihalf.com>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <8885da65-2d0f-ac2b-00c1-8ba6230ca9a8@redhat.com>
Date: Wed, 31 Jul 2019 13:37:19 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <1564554319-26810-1-git-send-email-mw@semihalf.com>
X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Wed, 31 Jul 2019 11:37:22 +0000 (UTC)
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit

On 07/31/19 08:25, Marcin Wojtas wrote:
> Until now, during the USB device enumeration when its PortState
> USB_PORT_STAT_CONNECTION bit was not set, the stack was not informed
> that the device is not present. Fix that by returning appropriate
> error code.
> 
> Change-Id: I588f82b987993e9755f64ce76cde9eb690ef1d54
> Signed-off-by: Marcin Wojtas <mw@semihalf.com>
> ---
>  MdeModulePkg/Bus/Usb/UsbBusDxe/UsbEnumer.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/MdeModulePkg/Bus/Usb/UsbBusDxe/UsbEnumer.c b/MdeModulePkg/Bus/Usb/UsbBusDxe/UsbEnumer.c
> index be9d9bd..ab1db15 100644
> --- a/MdeModulePkg/Bus/Usb/UsbBusDxe/UsbEnumer.c
> +++ b/MdeModulePkg/Bus/Usb/UsbBusDxe/UsbEnumer.c
> @@ -719,6 +719,7 @@ UsbEnumerateNewDev (
>  
>    if (!USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_CONNECTION)) {
>      DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: No device present at port %d\n", Port));
> +    Status = EFI_NOT_FOUND;
>      goto ON_ERROR;
>    } else if (USB_BIT_IS_SET (PortState.PortStatus, USB_PORT_STAT_SUPER_SPEED)){
>      Child->Speed      = EFI_USB_SPEED_SUPER;
> 

I think the patch is correct, based on a quite superficial analysis (i.e. without actual knowledge of USB specifics on my part).

The reason is that Status is EFI_SUCCESS when the "goto" statement is reached, due to the preceding context

  Status = HubApi->GetPortStatus (HubIf, Port, &PortState);

  if (EFI_ERROR (Status)) {
    DEBUG ((EFI_D_ERROR, "UsbEnumerateNewDev: failed to get speed of port %d\n", Port));
    goto ON_ERROR;
  }

And, the ON_ERROR label is documented as:

ON_ERROR:
  //
  // If reach here, it means the enumeration process on a given port is interrupted due to error.
  // [...]
  //
  return Status;

We shouldn't report success when there is no device present on the port.

I think EFI_NOT_FOUND is a suitable error code; while it is not listed explicitly in the leading comment on the function, it does fit under

  @retval Others                Failed to enumerate the device.

Marcin, can you please remove the "Change-Id" tag from the commit message? (Or the MdeModulePkg maintainers could do that, just before they push the patch.)

With "Change-Id" removed:

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo