From: tony@atomide•com (Tony Lindgren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry
Date: Mon, 13 Jul 2015 06:19:02 -0700 [thread overview]
Message-ID: <20150713131902.GH26485@atomide.com> (raw)
In-Reply-To: <20150707115819.GF12087@pali>
* Pali Roh?r <pali.rohar@gmail•com> [150707 05:00]:
> On Tuesday 07 July 2015 12:32:13 Russell King - ARM Linux wrote:
> > On Mon, Jul 06, 2015 at 10:26:13PM +0200, Pali Roh?r wrote:
> > > Legacy bootloaders can pass additional information for kernel or legacy
> > > userspace applications. When booting DT kernel then ATAGs structure is not
> > > more visible after running kernel uncompress code. This patch stores full
> > > ATAGs structure into DT "/chosen/linux,atags" entry, so kernel can later
> > > reuse it and export via /proc/atags to userspace.
> >
> > I think you need to go through your commit messages and improve them,
> > especially the ones with "TODO" in them. As long as there's still things
> > to be done, they're obviously not ready for merging.
> >
>
> I know, in cover letter email I wrote that documentation is not ready...
> I send patches for review and comments (like yours). I think it is still
> better to send something and mark it as incomplete. It could prevent to
> work on something which will be again rewritten...
>
> > Moreover, exporting the ATAGS is questionable, even _if_ there are non-
> > kexec programs making use of this. The ATAGs have _never_ been exported
> > to userspace when kexec disabled is the kernel - it was introduced for
> > kexec, and has always had this:
> >
> > config ATAGS_PROC
> > bool "Export atags in procfs"
> > depends on ATAGS && KEXEC
> > default y
> >
> > Now, the fact that someone decided to start using it is pretty sad,
> > because it means that if you disable KEXEC, userspace breaks. That's
> > not a kernel regression in any shape or form, because /proc/atags has
> > never been there without KEXEC enabled. That's a userspace bug, plain
> > and simple.
> >
> > Given that, I'm in two minds about whether to accept the last two
> > patches which make this more than just "for KEXEC use to enable a KEXEC
> > kernel to be booted."
> >
> > Had it been provided without the KEXEC conditional, then I don't have
> > a problem with these two patches.
> >
>
> I understand it. Nokia originally invented their own entries in /proc/
> which export needed ATAGs from kernel in human-readable form, but all
> those entries were non-standard and specific for Nokia's kernels.
>
> Do you have some other idea how to provide ATAGs information created
> dynamically by legacy closed proprietary bootloader to userspace from DT
> booted kernel?
>
> Anyway, for supporting kexec (with passing ATAGs) it is needed to have
> working /proc/atags file, right?
Yeah I think that since we already have it in /proc, we should just
support it. And keep it behind CONFIG_KEXEC and CONFIG_ARM_APPENDED_DTB
and hope we don't find other users for it.. Then reconsider the Kconfig
dependencies if we do find other users.
> > It also sets a precedent: by adding this into DT, it is creating a new
> > DT ABI as well, and we'll end up seeing dts files with an ATAG block
> > patched into them.
> >
> > Are the ATAGs at a fixed address on the N900?
>
> Yes, in board-rx51.c is:
>
> .atag_offset = 0x100
>
> and Nokia Bootloader (proprietary) store them to that address.
>
> > Can that be handled in
> > some kind of legacy file for the N900 which calls save_atags() on it, so
> > we don't end up introducing yet more stuff that we have to maintain into
> > the distant future? If not, what about copying a known working atag
> > structure into a legacy file for the N900?
>
> I already asked question if it is possible to read ATAGs from DT booted
> kernel. And somebody (do not remember who) wrote to ML, that it is not
> possible and it can be done in that uncompress code.
I guess the other option would be to keep the raw ATAG area reserved,
and only initialize /proc/atags from a board specific initcall.
But I think that would complicate the already fragile uncompress
relocation code even further?
Regards,
Tony
next prev parent reply other threads:[~2015-07-13 13:19 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-06 20:26 [PATCH 0/5] ATAGs to DT patches Pali Rohár
2015-07-06 20:26 ` [PATCH 1/5] arm: devtree: Set system_rev from DT "/revision" Pali Rohár
2015-12-24 19:02 ` Pali Rohár
2015-12-28 21:01 ` Frank Rowand
2015-12-28 22:27 ` Arnd Bergmann
2016-01-05 11:37 ` Pali Rohár
2016-01-05 11:45 ` Arnd Bergmann
2016-02-05 18:15 ` [PATCH] ARM: RX51: Set system_rev from ATAGS Ivaylo Dimitrov
2016-02-08 20:48 ` Tony Lindgren
2016-02-08 21:10 ` Pali Rohár
2016-02-09 16:17 ` Tony Lindgren
2016-02-10 18:23 ` [PATCH v1] " Ivaylo Dimitrov
2016-02-11 0:19 ` Tony Lindgren
2015-07-06 20:26 ` [PATCH 2/5] arm: boot: convert ATAG_REVISION to DT "/revision" entry Pali Rohár
2015-07-06 20:26 ` [PATCH 3/5] arm: atags: Fix declaration of function save_atags Pali Rohár
2015-07-06 20:26 ` [PATCH 4/5] arm: devtree: Read ATAGs structure from DT "/chosen/linux, atags" entry Pali Rohár
2015-07-06 20:26 ` [PATCH 5/5] arm: boot: store ATAGs structure into " Pali Rohár
2015-07-07 11:32 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Russell King - ARM Linux
2015-07-07 11:58 ` Pali Rohár
2015-07-13 13:19 ` Tony Lindgren [this message]
2015-10-12 20:16 ` Tony Lindgren
2015-10-12 20:25 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Pali Rohár
2015-10-12 20:45 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Tony Lindgren
2015-10-13 14:37 ` Pali Rohár
2015-11-05 11:40 ` Pali Rohár
2015-11-05 16:17 ` Tony Lindgren
2015-11-12 1:10 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Frank Rowand
2015-11-22 6:51 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Pavel Machek
2015-11-23 14:45 ` Pali Rohár
2015-11-25 18:16 ` Tony Lindgren
2015-11-25 19:48 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Arnd Bergmann
2015-11-25 21:03 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Tony Lindgren
2015-11-25 21:29 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Arnd Bergmann
2015-11-25 21:44 ` Pali Rohár
2015-11-25 21:51 ` Arnd Bergmann
2015-11-25 22:00 ` Pali Rohár
2015-11-26 4:19 ` Frank Rowand
2015-11-26 9:07 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Pali Rohár
2015-11-26 20:39 ` Tony Lindgren
2015-11-26 21:12 ` Ivaylo Dimitrov
2015-11-27 8:38 ` Pali Rohár
2015-11-27 8:44 ` Michael Trimarchi
2015-11-27 8:52 ` Michael Trimarchi
2015-11-27 14:51 ` Tony Lindgren
2015-11-27 13:27 ` Russell King - ARM Linux
2015-11-27 19:51 ` Russell King - ARM Linux
2015-11-27 21:06 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Arnd Bergmann
2015-11-27 23:28 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Nicolas Pitre
2015-11-28 12:27 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Arnd Bergmann
2015-11-28 12:54 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Russell King - ARM Linux
2015-11-28 12:33 ` Russell King - ARM Linux
2015-11-28 17:34 ` Nicolas Pitre
2015-11-28 21:02 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Frank Rowand
2015-11-29 18:09 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Russell King - ARM Linux
2015-11-29 18:19 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Pali Rohár
2015-11-29 23:13 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Russell King - ARM Linux
2015-11-30 0:09 ` Nicolas Pitre
2015-11-30 0:15 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Pali Rohár
2015-11-30 15:23 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Tony Lindgren
2015-11-30 15:39 ` Pali Rohár
2015-11-30 16:09 ` Nicolas Pitre
2015-12-15 9:33 ` Pali Rohár
2015-12-15 11:04 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux, atags" entry Arnd Bergmann
2015-12-15 12:20 ` [PATCH 5/5] arm: boot: store ATAGs structure into DT "/chosen/linux,atags" entry Russell King - ARM Linux
2015-12-15 17:24 ` Nicolas Pitre
2015-12-23 14:54 ` Ivaylo Dimitrov
2015-11-28 4:06 ` [PATCH 0/5] ATAGs to DT patches Frank Rowand
2015-11-28 5:55 ` Frank Rowand
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