linux-kernel - Re: [PATCH] usb: cp210x: Added support for GPIO (CP2103/4/5)

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Message-ID: <20381.15336.604590.461744@elektron.ikp.physik.tu-darmstadt.de>
Date:	Sun, 29 Apr 2012 15:02:32 +0200
From:	Uwe Bonnes <bon@...ktron.ikp.physik.tu-darmstadt.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] usb: cp210x: Added support for GPIO (CP2103/4/5)

>>>>> "Alan" == Alan Cox <alan@...rguk.ukuu.org.uk> writes:

    Alan> On Sat, 28 Apr 2012 20:17:07 +0200 Uwe Bonnes
    Alan> <bon@...ktron.ikp.physik.tu-darmstadt.de> wrote:

    >> >>>>> "Alan" == Alan Cox <alan@...rguk.ukuu.org.uk> writes:
    >> 
    >> ...
    Alan> The other question is whether having some custom gpio poking
    Alan> interface is actually a good idea. I suspect probably not. The
    Alan> kernel gpio layer can help a bit but doesn't really solve the
    Alan> problem as there is no way to tie a gpio to a port. Given how many
    Alan> devices seem to have gpios these days I wonder if we need a gpio
    Alan> setting interface via termiox.
    >>  Is this really kernel stuff or better handled in libusb(x)

    Alan> Tricky to do it that way when the kernel driver owns the
    Alan> interface. Also it's looking increasingly like we'll need to
    Alan> support a variety of "serial and a couple of extra magic lines"
    Alan> type interfaces for things like SIM readers.

Well,

most RS232/USB Adapter don't supply and most applications working with these
adapters don't need hard realtime. So even writing and reading the serial
lines can be handled with libusb, like libftdi does.

But as soon as higher level protocols based on the serial line get involved,
a kernel driver is needed...

So when thinking some termiox, some thoughts for the FTDI special modes,
like MPSSE or synchronous FIFO should be spent. It would come handy if I
could open /dev/ttyUSBx, set som termiox and could use the kernel driver for
sending and receiving MPSSE commands. MPSSE is e.g. used in OpenOCD and
xc3sprog to talk e.g. JTAG to external devices.

Bye 
-- 
Uwe Bonnes                bon@...ktron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
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