This is the structure being returned:
struct usbmon_packet {
u64 id; /* 0: URB ID - from submission to callback */
unsigned char type; /* 8: Same as text; extensible. */
unsigned char xfer_type; /* ISO (0), Intr, Control, Bulk (3) */
unsigned char epnum; /* Endpoint number and transfer direction */
unsigned char devnum; /* Device address */
u16 busnum; /* 12: Bus number */
char flag_setup; /* 14: Same as text */
char flag_data; /* 15: Same as text; Binary zero is OK. */
s64 ts_sec; /* 16: gettimeofday */
s32 ts_usec; /* 24: gettimeofday */
int status; /* 28: */
unsigned int length; /* 32: Length of data (submitted or actual) */
unsigned int len_cap; /* 36: Delivered length */
unsigned char setup[8]; /* 40: Only for Control 'S' */
}; /* 48 bytes total */
I'm not too keen on using an ASCII 'S' in the setup field to tell
whether setup[8] is in use or not. Am I correct in thinking that
setup[8] is always active on an URB submission and never active on a
completion or error? If that is the case then the flag_setup field is
redundant with the type field and can be eliminated. I would then make
the setup[8] presence variable depending on the packet type.
I also think flag_data is redundant based on the packet type, but I'm
not sure yet.
status looks to be active only on an error completion so the field
could be a union with setup[8].
The protocol can be further compressed by not including these fields:
xfer_type, epnum, devnum, busnum in completion/error packets. I
already have to track the URB submissions in order to decode the
protocol so I have these fields from the submission packet and they
can't change assuming that I'm understanding everything correctly.
--
Jon Smirl
[EMAIL PROTECTED]
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