On Sat, 10 Jun 2006, Pete Zaitcev wrote:
> The usbmon's documentation leaves me dissatisfied, it seems clumsy.
> What do you native English speaker guys think about the below, is
> it any improvement?
Here is an edited version of your patch. I didn't update any lines of the
document other than the ones you had changed. Native English speakers
will probably find this a little easier to read.
Alan Stern
Index: usb-2.6/Documentation/usb/usbmon.txt
===================================================================
--- usb-2.6.orig/Documentation/usb/usbmon.txt
+++ usb-2.6/Documentation/usb/usbmon.txt
@@ -97,20 +97,25 @@ Here is the list of words, from left to
Zi Zo Isochronous input and output
Ii Io Interrupt input and output
Bi Bo Bulk input and output
- Device address and Endpoint number are decimal numbers with leading zeroes
- or 3 and 2 positions, correspondingly.
-- URB Status. This field makes no sense for submissions, but is present
- to help scripts with parsing. In error case, it contains the error code.
- In case of a setup packet, it contains a Setup Tag. If scripts read a number
- in this field, they proceed to read Data Length. Otherwise, they read
- the setup packet before reading the Data Length.
+ Device address and Endpoint number are 3-digit and 2-digit (respectively)
+ decimal numbers, with leading zeroes.
+- URB Status. In most cases, this field contains a number, sometimes negative,
+ which represents a "status" field of the URB. This field makes no sense for
+ submissions, but is present anyway to help scripts with parsing. When an
+ error occurs, the field contains the error code. In case of a submission of
+ a Control packet, this field contains a Setup Tag instead of an error code.
+ It is easy to tell whether the Setup Tag is present because it is never a
+ number. Thus if scripts find a number in this field, they proceed to read
+ Data Length. If they find something else, like a letter, they read the setup
+ packet before reading the Data Length.
- Setup packet, if present, consists of 5 words: one of each for bmRequestType,
bRequest, wValue, wIndex, wLength, as specified by the USB Specification 2.0.
These words are safe to decode if Setup Tag was 's'. Otherwise, the setup
packet was present, but not captured, and the fields contain filler.
-- Data Length. This is the actual length in the URB.
+- Data Length. For submissions, this is the requested length. For callbacks,
+ this is the actual length.
- Data tag. The usbmon may not always capture data, even if length is nonzero.
- Only if tag is '=', the data words are present.
+ The data words are present only if this tag is '='.
- Data words follow, in big endian hexadecimal format. Notice that they are
not machine words, but really just a byte stream split into words to make
it easier to read. Thus, the last word may contain from one to four bytes.
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