Subject: Re: [PATCH] powerpc: Fix mem= cmdline handling on arch/powerpc for !MULTIPLATFORM

From: Michael Ellerman <[email-masked]>
Date: Sat, 25 Feb 2006 11:12:33 +1100

On Sat, 25 Feb 2006 10:18, Kumar Gala wrote:
> On Sat, 25 Feb 2006, Michael Ellerman wrote:
> > On Sat, 25 Feb 2006 09:43, Kumar Gala wrote:
> > > On Feb 24, 2006, at 4:27 PM, Michael Ellerman wrote:
> > > > Hi Kumar,
> > > >
> > > > On Sat, 25 Feb 2006 03:54, Kumar Gala wrote:
> > > >> mem= command line option was being ignored in arch/powerpc if we
> > > >> were not
> > > >> a CONFIG_MULTIPLATFORM (which is handled via prom_init stub). The
> > > >> initial
> > > >> command line extraction and parsing needed to be moved earlier in
> > > >> the boot
> > > >> process and have code to actual parse mem= and do something about
> > > >> it.
> > > >>
> > > >> @@ -1004,6 +991,41 @@ static int __init early_init_dt_scan_cho
> > > >>                 crashk_res.end = crashk_res.start + *lprop - 1;
> > > >>  #endif
> > > >>
> > > >> +	/* Retreive command line */
> > > >> + 	p = of_get_flat_dt_prop(node, "bootargs", &l);
> > > >> +	if (p != NULL && l > 0)
> > > >> +		strlcpy(cmd_line, p, min((int)l, COMMAND_LINE_SIZE));
> > > >> +
> > > >> +#ifdef CONFIG_CMDLINE
> > > >> +	if (l == 0 || (l == 1 && (*p) == 0))
> > > >> +		strlcpy(cmd_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
> > > >> +#endif /* CONFIG_CMDLINE */
> > > >> +
> > > >> +	DBG("Command line is: %s\n", cmd_line);
> > > >> +
> > > >> +	if (strstr(cmd_line, "mem=")) {
> > > >> +		char *p, *q;
> > > >> +		unsigned long maxmem = 0;
> > > >> +
> > > >> +		for (q = cmd_line; (p = strstr(q, "mem=")) != 0; ) {
> > > >> +			q = p + 4;
> > > >> +			if (p > cmd_line && p[-1] != ' ')
> > > >> +				continue;
> > > >> +			maxmem = simple_strtoul(q, &q, 0);
> > > >> +			if (*q == 'k' || *q == 'K') {
> > > >> +				maxmem <<= 10;
> > > >> +				++q;
> > > >> +			} else if (*q == 'm' || *q == 'M') {
> > > >> +				maxmem <<= 20;
> > > >> +				++q;
> > > >> +			} else if (*q == 'g' || *q == 'G') {
> > > >> +				maxmem <<= 30;
> > > >> +				++q;
> > > >> +			}
> > > >> +		}
> > > >> +		memory_limit = maxmem;
> > > >> +	}
> > > >> +
> > > >
> > > > Why not make the mem= parsing an early_param() handler and then call
> > > > parse_early_param() here?
> > >
> > > This would put constraints on the early_param()'s that I dont think
> > > we should impose.
> >
> > All they should really be doing is parsing the string and setting some
> > variables, so that seems reasonable to me. Is there anything in
> > particular?
>
> If you ever had to do some memory allocation as part of the parsing that
> might be an issue, since we haven't setup the LMB at that point.

Sure, but I think it's reasonable to say "don't allocate memory in an 
early_param handler", it is an _early_ param after all. But I guess we'll 
have to agree to disagree until someone else chimes in with an opinion :)

cheers

-- 
Michael Ellerman
IBM OzLabs

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person