From: arnd@arndb•de (Arnd Bergmann)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] serial: DCC(JTAG) serial and console emulation support
Date: Wed, 13 Oct 2010 21:45:30 +0200 [thread overview]
Message-ID: <201010132145.30550.arnd@arndb.de> (raw)
In-Reply-To: <1286993315.28336.10.camel@c-dwalke-linux.qualcomm.com>
On Wednesday 13 October 2010 20:08:35 Daniel Walker wrote:
> On Wed, 2010-10-13 at 19:44 +0200, Arnd Bergmann wrote:
> > On Wednesday 13 October 2010 18:17:03 Daniel Walker wrote:
> > > > I think you would be much better off making it a "hvc" driver, where
> > > > you just need to provide a read character and write character function
> > > > and an optional interrupt handler but otherwise have the common hvc
> > > > code take care of polling the hardware and talking to the tty layer.
> > >
> > > I don't know what the "hvc" driver is "Hypervisor Virtual Console"
> > > maybe?
> >
> > Yes, it originally was used only on hypervisors that had simple
> > read/write type consoles, but has now turned into a generic facility
> > that is used by a number of consoles that don't look like classic
> > serial ports.
> >
> > > Can you give any sort of example driver which does what you
> > > suggesting?
> >
> > Look at drivers/char/hvc_tile.c for the simplest case or
> > drivers/char/hvc_vio.c for one that uses interrupts.
>
> I found it independently actually .. It looks like there's at least two
> problems. This jtag driver has a status register which flags when RX is
> available, and TX is possible. I'm not sure this status register fits
> into the model.
I think that is how they all work. The read/write functions simply return
the number of characters transferred, which may be zero if the output
is busy or the input is empty.
> The other thing is that we have a ttyJ registered for
> this driver, and it would be nice to use that over something like ttyHVC
> (I'm not sure if that name is correct, just a guess).
It's hvc0, but I don't see this as a problem because the driver was never
upstream before -- you don't really get to complain about compatibility
with out-of-tree code :-)
Seriously, I don't think you need it, but if you really do, we can probably
find a way to work around this by changing the base hvc driver.
Arnd
next prev parent reply other threads:[~2010-10-13 19:45 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-05 19:07 [PATCH] serial: DCC(JTAG) serial and console emulation support Daniel Walker
2010-10-06 2:55 ` Nicolas Pitre
2010-10-06 13:48 ` Daniel Walker
2010-10-06 14:22 ` Nicolas Pitre
2010-10-06 14:49 ` Daniel Walker
2010-10-06 15:21 ` Nicolas Pitre
2010-10-06 15:33 ` Daniel Walker
2010-10-06 15:47 ` Nicolas Pitre
2010-10-06 15:54 ` Daniel Walker
2010-10-06 16:22 ` Nicolas Pitre
2010-10-06 16:40 ` Daniel Walker
2010-10-06 17:02 ` Nicolas Pitre
2010-10-06 17:07 ` Daniel Walker
2010-10-07 21:27 ` Tony Lindgren
2010-10-07 21:58 ` Daniel Walker
2010-10-08 1:28 ` Nicolas Pitre
2010-10-08 20:35 ` Tony Lindgren
2010-10-08 20:59 ` Tony Lindgren
2010-10-08 21:27 ` Nicolas Pitre
2010-10-08 20:36 ` Tony Lindgren
2010-10-08 1:25 ` Nicolas Pitre
2010-10-08 20:32 ` Tony Lindgren
2010-10-08 20:58 ` Tony Lindgren
2010-10-08 21:28 ` Nicolas Pitre
2010-10-08 21:25 ` Nicolas Pitre
2010-10-08 21:49 ` Tony Lindgren
2010-10-09 0:57 ` Nicolas Pitre
2010-10-13 15:21 ` Arnd Bergmann
2010-10-13 16:17 ` Daniel Walker
2010-10-13 17:44 ` Arnd Bergmann
2010-10-13 18:08 ` Daniel Walker
2010-10-13 19:45 ` Arnd Bergmann [this message]
2010-10-13 19:52 ` Daniel Walker
2010-10-13 20:10 ` Arnd Bergmann
2010-10-13 20:24 ` Daniel Walker
2010-10-13 20:44 ` Nicolas Pitre
2010-10-13 20:49 ` Daniel Walker
2010-10-13 22:51 ` Nicolas Pitre
2010-10-13 23:26 ` Russell King - ARM Linux
2010-10-13 23:41 ` Nicolas Pitre
2010-10-13 19:55 ` Nicolas Pitre
2010-10-13 20:00 ` Daniel Walker
2010-10-13 20:27 ` Nicolas Pitre
2010-10-13 20:47 ` Daniel Walker
2010-10-13 22:05 ` Daniel Walker
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