On Mon, 28 Nov 2005, David Brownell wrote:
> On Sunday 27 November 2005 9:15 am, Alan Stern wrote:
> >
> > So far as I know, the USB API doesn't allow for size limits on URB
> > transfer lengths. There's no mechanism to report back that an URB is too
> > large,
>
> Sure there is ... return "-EMSGSIZE" from usb_submit_urb(); or perhaps
> some other errno value. The API clearly allows for that fault code. :)
>From Documentation/usb/error-codes.txt:
-EMSGSIZE (a) endpoint maxpacket size is zero; it is not usable
in the current interface altsetting.
(b) ISO packet is biger than endpoint maxpacket
(c) requested data transfer size is invalid (negative)
There's nothing about an URB's transfer_length being too big.
> > and no driver tries to break URBs up into smaller pieces.
>
> True, but that's a different issue. Few drivers bother looking at the
> fault codes reported by usbcore or the HCDs ... that'd basically be a
> bug in the driver.
Even the ones that do check the fault codes don't try to subdivide URBs.
Alan Stern
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