Messages in this thread | | | From | Michal Nazarewicz <> | Subject | Re: [PATCH v4 3/4] usb: ffs: check quirk to pad epout buf size when not aligned to maxpacketsize | Date | Fri, 08 Nov 2013 13:23:32 +0100 |
| |
On Thu, Nov 07 2013, Alan Stern wrote: > What happens if the userspace daemon writes to epfile but the host > changes the config or altsetting before all the data can be sent? Does > the remaining data get flushed?
Each read and write is mapped to a single request, so the usual.
> I'm still a little unclear on this. Disabling the function ought to > have much the same effect as changing the config or altsetting: Writes > to endpoint files should be flushed and reads should be terminated. > Otherwise you would end up sending stale data to the host or reading > data that the daemon isn't prepared for.
You may have a point here. I'll try to prepare a patch over the weekend.
> Given that, there doesn't seem to be any need for a loop. Copy the > data; if the function was disabled in the meantime then throw away the > data and return an appropriate error code.
Right.
> I don't see any reason why you should ever have to copy the same data > from userspace multiple times.
That actually never happens. The data is copied at most once.
-- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +--<mpn@google.com>--<xmpp:mina86@jabber.org>--ooO--(_)--Ooo-- [unhandled content-type:application/pgp-signature] | |