On Sat, Jan 19, 2008 at 10:09:47PM -0800, Matthew Dharm wrote:
> On Sat, Jan 19, 2008 at 09:25:57PM -0700, Grant Grundler wrote:
> > Hi,
> > I'm slightly confused by this declaration in drivers/usb/storage/usb.c:
> > #define UNUSUAL_DEV(id_vendor, id_product, bcdDeviceMin, bcdDeviceMax, \
> > vendorName, productName,useProtocol, useTransport, \
> > initFunction, flags) \
> > ...
> >
> > and in unusual.h:
> > UAL_DEV( 0x03eb, 0x2002, 0x0100, 0x0100,
> > "ATMEL",
> > "SND1 Storage",
> > US_SC_DEVICE, US_PR_DEVICE, NULL,
> > US_FL_IGNORE_RESIDUE),
> >
> > So US_SC_DEVICE ("Sub Classes" per include/linux/usb_usual.h) is used as a
> > wild card for useProtocol and US_PR_DEVICE ("Protocols") is the wildcard
> > for useTransport?
>
>
> No, they aren't wildcards.
>
> The value means "use whatever the device presents". It's not used as a
> matching parameter. Matching only happens on VID/PID and revision.
Sorry - "wildcards" was a poor choice of words.
> Also, the naming is goofy for a reason. The USB spec calls the numbers
> "SubClass" and "Protocol". However, the way they are used, the SubClass
> defines the protocol (i.e. language) the device uses; the "Protocol"
> defines the transport (i.e. how messages are packed for exchange).
>
> There is no USB-spec field named 'Transport'.
Thanks for the excellent, concise explanation.
I've proposed a patch below to help capture some of it.
I just want to "connect the dots" between the related code.
thanks,
grant
Signed-off-by: Grant Grundler <[EMAIL PROTECTED]>
--- include/linux/usb_usual.h-ORIG 2007-10-09 13:31:38.000000000 -0700
+++ include/linux/usb_usual.h 2008-01-20 00:00:30.000000000 -0800
@@ -69,7 +69,7 @@
* But it's the only header included into all places which need them.
*/
-/* Sub Classes */
+/* Sub Classes - defines which Protocol will be used */
#define US_SC_RBC 0x01 /* Typically, flash devices */
#define US_SC_8020 0x02 /* CD-ROM */
@@ -83,7 +83,7 @@
#define US_SC_DEVICE 0xff /* Use device's value */
-/* Protocols */
+/* Protocols - defines which transport used (how messages are packed) */
#define US_PR_CBI 0x00 /* Control/Bulk/Interrupt */
#define US_PR_CB 0x01 /* Control/Bulk w/o interrupt */
>
> Matt
>
> --
> Matthew Dharm Home: [EMAIL PROTECTED]
> Maintainer, Linux USB Mass Storage Driver
>
> You were using cheat codes too. You guys suck.
> -- Greg to General Studebaker
> User Friendly, 12/16/1997
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