Re: [PATCH v4 3/4] usb: ffs: check quirk to pad epout buf size when not aligned to maxpacketsize
From: Michal Nazarewicz
Date: Fri Nov 08 2013 - 07:23:51 EST
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, MichaÅ âmina86â Nazarewicz (o o)
ooo +--<mpn@xxxxxxxxxx>--<xmpp:mina86@xxxxxxxxxx>--ooO--(_)--Ooo--
Attachment:
signature.asc
Description: PGP signature