On Wed, Jul 02 2014, David Laight <david.lai...@aculab.com> wrote:
> From: Andrzej Pietrasiewicz
>> Sent: 02 July 2014 12:20
>> To: linux-usb@vger.kernel.org; Michal Nazarewicz; Felipe Balbi; Greg
>> Kroah-Hartman; Marek Szyprowski
>> Subject: Re: [PATCH] usb: gadget: f_fs: OS descriptors support
>>
>> W dniu 02.07.2014 13:04, Peter Stuge pisze:
>> > Andrzej Pietrasiewicz wrote:
>> >> +++ b/include/uapi/linux/usb/functionfs.h
>> >> @@ -33,6 +32,42 @@ struct usb_endpoint_descriptor_no_audio {
>> > ..
>> >> +/* MS OS Extended Compatibility Descriptor header */
>> >> +struct usb_ext_compat_desc_header {
>> >> + struct usb_os_desc_header header;
>> >> + __u8 bCount;
>> >> + __u8 Reserved;
>> >> +} __attribute__((packed));
>> >> +
>> >> +struct usb_ext_compat_desc {
>> >> + __u8 bFirstInterfaceNumber;
>> >> + __u8 Reserved1;
>> >> + __u8 CompatibleID[8];
>> >> + __u8 SubCompatibleID[8];
>> >> + __u8 Reserved2[6];
>> >> +};
>> >
>> > Shouldn't usb_ext_compat_desc be packed too, like all the others?
>> >
>> Good catch, thanks!
>
> In this case it is completely pointless - all the fields are byte aligned.
>
> Alternatively it shouldn't be 'packed', and a full audit of the
> other structures done to determine which ones can ever be misaligned
> and then determine whether that should actually be allowed.
All of the structures describe a wire protocol, whether we thing the
structure can be allowed or not is inconsequential since that's what is
being used. All of those structures must be packed.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
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