[PATCH] USB: Patch to make usbmon to print control setup packets

Make usbmon to print Setup packets of Control transfers. This is useful
when debugging enumeration issues.

This is a change to the trace format which is not fully compatible.
A parser has to look at the data length word now. If that word is
a character like 's', read setup packet before proceeding with data.
I decided not to bump the API tag for this because not many such
parsers exist at this point.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 21 insertions, 8 deletions

diff --git a/Documentation/usb/usbmon.txt b/Documentation/usb/usbmon.txt
index 2f8431f92b7..f1896ee3bb2 100644
--- a/Documentation/usb/usbmon.txt
+++ b/Documentation/usb/usbmon.txt
@@ -101,6 +101,13 @@ Here is the list of words, from left to right:
   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, the proceed to read Data Length. Otherwise, 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 tag. The usbmon may not always capture data, even if length is nonzero.
   Only if tag is '=', the data words are present.
@@ -125,25 +132,31 @@ class ParsedLine {
                         String data_str = st.nextToken();
                         int len = data_str.length() / 2;
                         int i;
+                        int b;  // byte is signed, apparently?! XXX
                         for (i = 0; i < len; i++) {
-                                data[data_len] = Byte.parseByte(
-                                    data_str.substring(i*2, i*2 + 2),
-                                    16);
+                                // data[data_len] = Byte.parseByte(
+                                //     data_str.substring(i*2, i*2 + 2),
+                                //     16);
+                                b = Integer.parseInt(
+                                     data_str.substring(i*2, i*2 + 2),
+                                     16);
+                                if (b >= 128)
+                                        b *= -1;
+                                data[data_len] = (byte) b;
                                 data_len++;
                         }
                 }
         }
 }
 
-This format is obviously deficient. For example, the setup packet for control
-transfers is not delivered. This will change in the future.
+This format may be changed in the future.
 
 Examples:
 
-An input control transfer to get a port status:
+An input control transfer to get a port status.
 
-d74ff9a0 2640288196 S Ci:001:00 -115 4 <
-d74ff9a0 2640288202 C Ci:001:00 0 4 = 01010100
+d5ea89a0 3575914555 S Ci:001:00 s a3 00 0000 0003 0004 4 <
+d5ea89a0 3575914560 C Ci:001:00 0 4 = 01050000
 
 An output bulk transfer to send a SCSI command 0x5E in a 31-byte Bulk wrapper
 to a storage device at address 5: