From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Fri, 19 Apr 2013 17:22:26 +0100 Subject: [RFC] arm64: Early printk support for virtio-mmio console devices. In-Reply-To: References: <20130419090558.GA13283@mudshark.cambridge.arm.com> <20130419092752.GB13283@mudshark.cambridge.arm.com> <20130419093953.GD13283@mudshark.cambridge.arm.com> <20130419161201.GA5383@localhost.cambridge.arm.com> Message-ID: <20130419162226.GB5383@localhost.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Apr 19, 2013 at 05:14:36PM +0100, Peter Maydell wrote: > On 19 April 2013 17:12, Catalin Marinas wrote: > > On Fri, Apr 19, 2013 at 11:05:47AM +0100, Peter Maydell wrote: > >> Please make the kernel pick the device out of the device tree > >> blob. The whole point of device tree is that it's how to tell > >> the kernel where things live -- making kvmtool/QEMU and/or the > >> user also have to mess with the kernel command line is awkward > >> and annoying. > > > > For a normal console device, it indeed needs to get it from the DT. For > > early console, you want it earlier than DT parsing so we pass it on the > > kernel command line via the earlyprintk= parameter. > > You should fix your DT handling code so you can get at the info > when you need it rather than pushing the problem into bootloaders > and QEMU, please. DT is your data structure so feel free to > (re)design it so relevant information can be accessed early > if that's useful. earlyprintk is used for debugging early problems, like DT parsing. You don't have to use it unless you are debugging something. Without earlyprintk you just get a normal console during boot, based on the DT description. -- Catalin