From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH v3 -next 11/11] serial: 8250_early: Remove setup_early_serial8250_console() Date: Fri, 03 Apr 2015 14:27:30 -0400 Message-ID: <551EDB92.9070008@hurleysoftware.com> References: <1425932842-21812-1-git-send-email-peter@hurleysoftware.com> <1425932842-21812-12-git-send-email-peter@hurleysoftware.com> <551CB5DF.1010108@hurleysoftware.com> <551D6EEA.6050704@hurleysoftware.com> <551E6D61.7000501@hurleysoftware.com> <551ED011.1030004@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Yinghai Lu Cc: Andrew Morton , Greg Kroah-Hartman , Linux Kernel Mailing List , Jiri Slaby , Rob Herring , "linux-serial@vger.kernel.org" List-Id: linux-serial@vger.kernel.org On 04/03/2015 01:44 PM, Yinghai Lu wrote: > On Fri, Apr 3, 2015 at 10:38 AM, Peter Hurley wrote: >> On 04/03/2015 12:57 PM, Yinghai Lu wrote: >> >> Wait -- you have earlycon in a product?? > > What do you mean? I mean, what will happen if I put in a big debug banner like Steven did for ftrace? Kernel developers need earlycon for debugging arch code; often the earlycon is just hacked together especially when it requires fixmap support. Putting it in a product and _relying on undocumented behavior_ is a bad idea. > when you are using "console=uart8250,io,0x3f8" > you will have earlycon at first, and handover to console. which means you have to have CONFIG_SERIAL_EARLYCON to get a serial console at all. I have no problem fixing this _if this is causing actual regressions_, and not simply some minor inconvenience that can be fixed by editing your grub command line. However, I see this undocumented behavior as a cautionary tale for why not every kernel command line hack should be accepted in mainline. Regards, Peter Hurley