Re: [Patch] MdeModulePkg/UsbMassStorageDxe: Verify Get Max LUN value

["Kinney, Michael D" <michael.d.kinney@intel.com>]

Star,

I do not recall the exact value I saw.

However, the spec states that one byte is returned
with the max LUN value.  It does not state that
the byte is composed of bitfields with the lower
bits being the max LUN, so I prefer the value
check instead if the and mask.

Thanks,

Mike
 

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org]
> On Behalf Of Zeng, Star
> Sent: Monday, November 13, 2017 2:03 AM
> To: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-
> devel@lists.01.org
> Cc: Dong, Eric <eric.dong@intel.com>; Zeng, Star
> <star.zeng@intel.com>
> Subject: Re: [edk2] [Patch]
> MdeModulePkg/UsbMassStorageDxe: Verify Get Max LUN value
> 
> Mike,
> 
> Just curious about what is the value returned for MaxLun
> in the case you met before this patch?
> 
> Could *MaxLun  &= USB_BOT_MAX_LUN work?
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: Zeng, Star
> Sent: Monday, November 13, 2017 5:45 PM
> To: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-
> devel@lists.01.org
> Cc: Dong, Eric <eric.dong@intel.com>; Zeng, Star
> <star.zeng@intel.com>
> Subject: RE: [Patch] MdeModulePkg/UsbMassStorageDxe:
> Verify Get Max LUN value
> 
> Reviewed-by: Star Zeng <star.zeng@intel.com>
> 
> How about also adding the compatibility info(now in
> commit log) to the code comments?
> For example,
> 
> +    //
> +    // If MaxLun is larger than the maximum LUN value
> (0x0f) supported by the
> +    // USB Mass Storage Class Bulk-Only Transport Spec,
> then set MaxLun to 0
> +    // which means no LUN is associated with the device.
> +    // It improves compatibility with USB FLASH drives
> that have a single LUN,
> +    // but return invalid maximum LUN values.
> +    //
> 
> Thanks,
> Star
> -----Original Message-----
> From: Kinney, Michael D
> Sent: Thursday, November 9, 2017 6:19 AM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Dong, Eric
> <eric.dong@intel.com>
> Subject: [Patch] MdeModulePkg/UsbMassStorageDxe: Verify
> Get Max LUN value
> 
> The USB Mass Storage Class Specification states that a
> maximum LUN value larger than 0x0F is invalid.  Add a
> check to make sure this maximum LUN value is in this
> valid range, and if it is not, then assume that the
> device does not support multiple LUNs and return a
> maximum LUN value of 0.
> 
> This change improves compatibility with USB FLASH drives
> that have a single LUN, but return invalid maximum LUN
> values.
> 
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Michael D Kinney
> <michael.d.kinney@intel.com>
> ---
>  MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c | 10
> +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git
> a/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
> b/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
> index 4bb7222b89..c7436cf036 100644
> --- a/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
> +++ b/MdeModulePkg/Bus/Usb/UsbMassStorageDxe/UsbMassBot.c
> @@ -2,7 +2,7 @@
>    Implementation of the USB mass storage Bulk-Only
> Transport protocol,
>    according to USB Mass Storage Class Bulk-Only
> Transport, Revision 1.0.
> 
> -Copyright (c) 2007 - 2011, Intel Corporation. All rights
> reserved.<BR>
> +Copyright (c) 2007 - 2017, Intel Corporation. All rights
> reserved.<BR>
>  This program and the accompanying materials  are
> licensed and made available under the terms and
> conditions of the BSD License  which accompanies this
> distribution.  The full text of the license may be found
> at @@ -576,6 +576,14 @@ UsbBotGetMaxLun (
>                              1,
>                              &Result
>                              );
> +  if (!EFI_ERROR (Status) && *MaxLun > USB_BOT_MAX_LUN)
> {
> +    //
> +    // If MaxLun is larger than the maximum LUN value
> (0x0f) supported by the
> +    // USB Mass Storage Class Bulk-Only Transport Spec,
> then set MaxLun to 0
> +    // which means no LUN is associated with the device.
> +    //
> +    *MaxLun = 0;
> +  }
> 
>    return Status;
>  }
> --
> 2.14.2.windows.3
> 
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