From mboxrd@z Thu Jan 1 00:00:00 1970 From: nico@fluxnic.net (Nicolas Pitre) Date: Wed, 13 Oct 2010 15:55:45 -0400 (EDT) Subject: [PATCH] serial: DCC(JTAG) serial and console emulation support In-Reply-To: <1286993315.28336.10.camel@c-dwalke-linux.qualcomm.com> References: <1286305668-19987-1-git-send-email-dwalker@codeaurora.org> <201010131721.39623.arnd@arndb.de> <1286986623.28336.3.camel@c-dwalke-linux.qualcomm.com> <201010131944.54135.arnd@arndb.de> <1286993315.28336.10.camel@c-dwalke-linux.qualcomm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 13 Oct 2010, 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. 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). Really? Is there a compelling reason to perpetuate this serial device namespace fragmentation nonsense? Your initial patch even had a config option to hijack /dev/ttyS0 because of that. Nicolas