From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 21 Nov 2008 11:23:14 +1100 From: David Gibson To: Timur Tabi Subject: Re: powerpc: udbg based backend for hvc_console Message-ID: <20081121002314.GA13049@yookeroo.seuss> References: <20081024035434.GF4267@yookeroo.seuss> <20081119004220.GE29577@yookeroo.seuss> <4569571e317d43f1b26b087fcdebcba3@bga.com> <4925B78B.2040709@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <4925B78B.2040709@freescale.com> Cc: linux-ppc , Milton Miller List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Nov 20, 2008 at 01:16:27PM -0600, Timur Tabi wrote: > Milton Miller wrote: > > > Stated differently, if your routine (1) fundamently works one character > > at a time and (2) is not interrupt driven, and (3) only supports one > > channel, what avantage is there to an explicit hvc driver? > > I think it's because HVC has the ability to use HVC client drivers > for console and TTY, but udbg does not. So if you have a udbg-only > driver, it will cease to function when the kernel switches to the > normal console. > > Perhaps it would make more sense to have the kernel continue to use udbg if > there is no normal console driver, instead of relying on David's > driver. This doesn't work - the udbg console can't support a full tty driver which is needed by userspace. Originally, I was going to extend the udbg console so that it supported a tty backended onto the udbg methods. Then I realised that the code I'd need to do this would be essentially identical to hvconsole, so why duplicate it. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson