linux-kernel - Re: [PATCH] usb: gadget: f_fs: Fix kernel panic for SuperSpeed

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Message-ID: <5729ADC9.3030704@nvidia.com>
Date:	Wed, 4 May 2016 16:07:37 +0800
From:	Jim Lin <jilin@...dia.com>
To:	Felipe Balbi <balbi@...nel.org>
CC:	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: gadget: f_fs: Fix kernel panic for SuperSpeed

On 2016年04月29日 19:57, Felipe Balbi wrote:
> * PGP Signed by an unknown key
>
>
> Hi,
>
> Jim Lin <jilin@...dia.com> writes:
>> On 2016年04月28日 20:21, Felipe Balbi wrote:
>>>> I also attach git log of system/core/adb/usb_linux_client.cpp of Android
>>>> N for your reference.
>>>> "
>>>> Author: Badhri Jagan Sridharan <Badhri@...gle.com>
>>>> Date:   Mon Oct 5 13:04:03 2015 -0700
>>>>
>>>>        adbd: Add os descriptor support for adb.
>>>>
>>>>        Eventhough windows does not rely on extended os
>>>>        descriptor for adbd, when android usb device is
>>>>        configures as a composite device such as mtp+adb,
>>>>        windows discards the extended os descriptor even
>>>>        if one of the USB function fails to send
>>>>        the extended compat descriptor. This results in automatic
>>>>        install of MTP driverto fail when Android device is in
>>>>        "File Transfer" mode with adb enabled.
>>>>
>>>> https://msdn.microsoft.com/en-us/library/windows/hardware/gg463179.aspx
>>>> "
>>> Okay, cool. Can you check that you're limitting your controller's speed
>>> to high-speed ?
>>>
>> Let's focus on original patch.
>> Could you help to explain why we need below d->Reserved1 checking?
>> Now the question is that
>>
>> https://msdn.microsoft.com/en-us/library/windows/hardware/gg463179.aspx
>>
>> Page 7 of OS_Desc_CompatID.doc
>> defines reserved field to be 1 and
>> below code will think that os_desc is invalid because d->Reserved1 is 1.
>>
>>
>> In f_fs.c
>> "
>> static int __ffs_data_do_os_desc(enum ffs_os_desc_type type,
>>                    struct usb_os_desc_header *h, void *data,
>>                    unsigned len, void *priv)
>> {
>>       struct ffs_data *ffs = priv;
>>       u8 length;
>>
>>       ENTER();
>>
>>       switch (type) {
>>       case FFS_OS_DESC_EXT_COMPAT: {
>>           struct usb_ext_compat_desc *d = data;
>>           int i;
>>
>>           if (len < sizeof(*d) ||
>>               d->bFirstInterfaceNumber >= ffs->interfaces_count ||
>>               d->Reserved1)
>>               return -EINVAL;
>> "
> that's fine, but this is only failing because something else is
> returning the wrong set of descriptors (SS vs HS). That's the bug we
> want to fix, not work around it.
>
Thanks.

--nvpublic