linux-kernel - Re: [PATCH v2 0/5] minitty: a minimal TTY layer alternative for embedded systems

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Date:   Tue, 04 Apr 2017 12:59:09 -0500
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Stuart Longland <stuartl@...glandclan.id.au>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Andi Kleen <andi@...stfloor.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 0/5] minitty: a minimal TTY layer alternative for
 embedded systems

On Tue, 2017-04-04 at 20:08 +0300, Andy Shevchenko wrote:
> On Tue, Apr 4, 2017 at 7:59 PM, Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
> > On Tue, 2017-04-04 at 00:05 +0300, Andy Shevchenko wrote:
> 
> > Yes, in a previous project, I had been working toward getting a < 1M
> > system to boot on Galileo hardware (which it did, but using more than
> > that - the Galileo2 has 256MB, but it was the target hardware at the
> > time, and I was hoping eventually to be able to boot out of the 512k
> > on-chip SRAM).
> >
> > I was focused at that point mainly on the kernel static size, and using
> > a combination of Josh Triplett's tinification tree, Andi Kleen's LTO and
> > net-diet patches, and my own miscellaneous patches that I was planning
> > on eventually upstreaming, I ended up with a system that I could boot to
> > shell with a 455k text size:
> >
> > Memory: 235636K/245176K available (455K kernel code, 61K rwdata,
> > 64K rodata, 132K init, 56K bss, 3056K reserved, 0K cma-reserved)
> >
> > virtual kernel memory layout:
> >     fixmap  : 0xfffe5000 - 0xfffff000   ( 104 kB)
> >     vmalloc : 0xd05f0000 - 0xfffe3000   ( 761 MB)
> >     lowmem  : 0xc0000000 - 0xcfdf0000   ( 253 MB)
> >       .init : 0xc1094000 - 0xc10b5000   ( 132 kB)
> >       .data : 0xc1071fac - 0xc1092760   ( 129 kB)
> >       .text : 0xc1000000 - 0xc1071fac   ( 455 kB)
> >
> > That was without networking.  Enabling networking added about 250k, and
> > at that point I could ssh in and run a webserver, still less than 1M as
> > far as kernel static size, which of course completely ignores the kernel
> > dynamic size and userspace.
> 
> Thanks for sharing your experience. The question closer to this
> discussion what did you do against TTY/UART/(related) layer(s)?
> 

I'd have to go back and take a look, but nothing special AFIAR.

No patches or hacks along those lines, and the only related thing I see
as far as config is:
	
	cfg/pty-disable.scc \

which maps to:

	# CONFIG_UNIX98_PTYS is not set