Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752690AbdDCTqN (ORCPT ); Mon, 3 Apr 2017 15:46:13 -0400 Received: from mail-io0-f195.google.com ([209.85.223.195]:33008 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752571AbdDCTqK (ORCPT ); Mon, 3 Apr 2017 15:46:10 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170401222119.25106-1-nicolas.pitre@linaro.org> <87pogur0y9.fsf@firstfloor.org> <92fb1e4a-d6df-f55b-c0a1-9c1eb78e3943@longlandclan.id.au> From: Geert Uytterhoeven Date: Mon, 3 Apr 2017 21:46:08 +0200 X-Google-Sender-Auth: lXOnUw70bVXs6UrTcDeIrhKjJHc Message-ID: Subject: Re: [PATCH v2 0/5] minitty: a minimal TTY layer alternative for embedded systems To: Rob Herring Cc: Stuart Longland , Nicolas Pitre , Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , Andi Kleen , "linux-serial@vger.kernel.org" , Jiri Slaby , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2325 Lines: 50 On Mon, Apr 3, 2017 at 8:57 PM, Rob Herring wrote: > On Mon, Apr 3, 2017 at 1:14 PM, Geert Uytterhoeven wrote: >> On Mon, Apr 3, 2017 at 12:44 AM, Stuart Longland >> wrote: >>> On 03/04/17 07:41, Nicolas Pitre wrote: >>>>> No PTYs seems like a big limitation. This means no sshd? >>>> Again, my ultimate system target is in the sub-megabyte of RAM. I >>>> really doubt you'll be able to fit an SSH server in there even if PTYs >>>> were supported, unless sshd (or dropbear) can be made really tiny. >>>> Otherwise you most probably have sufficient resources to run the regular >>>> TTY code. >>> >>> Are we talking small microcontrollers here? The smallest machine in >>> terms of RAM I ever recall running Linux on was a 386SX/25 MHz with 4MB >>> RAM, and that had a MMU. >> >> Let's halve that. I once tried and ran Linux in 2 MiB, incl. X, twm, and xterm. >> Of course with swap enabled. And swapping like hell. > > These are different target uses. We're talking about fixed function, > statically linked user space at the minimum (some may want no > userspace even). Applications that could use an RTOS instead but > benefit from the Linux hardware support, features and ecosystem. It's > not a whole new code base or environment to learn. Maybe Zephyr will > have traction and improve things, but projects I've been involved with > using RTOSs generally have discussions around needing to re-write the > crappy RTOS. Sure. I just wanted to point out that there was a time you could have _more_ than you need for small fixed function embedded systems in 2 MiB of RAM. > The absolute amount of RAM target is not so important. What's > important is getting to a size feasible for onchip RAM. That's always > moving (up), but has generally been out of reach for Linux. DigiKey shows 39 ARM SoCs with 1 MiB or more of RAM. But once you want 3 MiB or more, the lone winner is Renesas' RZ/A1 (up to 10 MiB). Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds