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Re: uvideo uvm_fault panic writes:

>+uvideo: truncated CS subtype-0x7 descriptor, length 30 < 38uvideo: unimplemented VS CS descriptor len=30 type=0x24 subtype=0x07

>        bLength                            30
>        bDescriptorType                    36
>        bDescriptorSubtype                  7 (FRAME_MJPEG)
>        bFrameIndex                         1
>        bmCapabilities                   0x01
>          Still image supported
>        wWidth                           1280
>        wHeight                           720
>        dwMinBitRate                442368000
>        dwMaxBitRate                442368000
>        dwMaxVideoFrameBufferSize     1843200
>        dwDefaultFrameInterval         333333
>        bFrameIntervalType                  1
>        dwFrameInterval( 0)            333333

The descriptors are pretty ugly to parse and the sanity checks
added are neither correct nor sufficient.

In this case, there is a

typedef union {
        uvideo_frame_interval_continuous_t      continuous;  
        uvideo_frame_interval_discrete_t        discrete;
} uvideo_frame_interval_t;

as a last element where uvideo_frame_interval_discrete_t is even
a variable length array, and all depends on the bFrameIntervalType.

The descriptor isn't padded for all possible types like a C union,
so validating against a sizeof doesn't work.

The result of course is that the formats are considered invalid
and there is no default format which the open routine assumes
to be valid without further checks...

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