From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw01.freescale.net (az33egw01.freescale.net [192.88.158.102]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw01.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 4DF12DDF03 for ; Mon, 8 Oct 2007 11:31:59 +1000 (EST) Message-ID: <47098882.1010900@freescale.com> Date: Sun, 07 Oct 2007 20:31:46 -0500 From: Scott Wood MIME-Version: 1.0 To: "Mark A. Greer" Subject: Re: [RFC] [PATCH] PowerPC: add more than 4MB kernel image size support to bootwarapper References: <20070924113627.GA30504@ru.mvista.com> <20070925022935.GI30338@localhost.localdomain> <46FD0E4D.30305@ru.mvista.com> <20071003055005.GD18978@localhost.localdomain> <20071005015849.GA9862@mag.az.mvista.com> <20071005173054.GA4295@loki.buserror.net> <20071005210320.GE6663@mag.az.mvista.com> In-Reply-To: <20071005210320.GE6663@mag.az.mvista.com> Content-Type: text/plain; charset=UTF-8; format=flowed Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Mark A. Greer wrote: > Why? Because its only safe to download a zImage to certain "safe" locations. > Where those "safe" locations are vary by firmware, firmware version, and > zImage size. This is the issue we're discussing. In theory, yes -- but in practice the odds of this particular heuristic choosing an unsuitable address seem slim. > I've already explained _why_ the link address matters WRT where its downloaded. Sorry, I was being a bit too pendantic with respect to the distinction between link and load address. >>> Also, being able to control the link address (that is, the download >>> address with some firmwares) is not a u-boot specific issue and we >>> shouldn't make a u-boot specific solution. >> How is this a u-boot specific solution? > > Because the hoops being jumped through in the patch(es) are to make > u-boot happy and no other firmware. No, the "hoops" (which I don't think are sufficiently complicated to warrant such a name) are to address a generic issue with the bootwrapper -- it wants to put the kernel at zero. It'd be really nice if, in the absense of a vmlinux_alloc method, the generic code would do an ordinary malloc() if there's not enough room at zero. >> I'd much rather it be automatic than require the user to guess an >> appropriate value (and be aware in the first place that it needs to be set). > > Sure, automatic is nice; conjuring up the magic to make it work in all > situations isn't. I think this heuristic would work in most situations, so if we do add a manual override it should be an override, and not something that everybody has to put up with. > Having the link address--and therefore the download address on some > systems--mysteriously and uncontrollably jump around based on the zImage > size is asking for trouble. It's a source of potential issues, but I think "asking for trouble" is exaggerating somewhat. -Scott