From: frank.rowand@am•sony.com (Frank Rowand)
To: linux-arm-kernel@lists•infradead.org
Subject: Request review of device tree documentation
Date: Fri, 18 Jun 2010 15:12:03 -0700 [thread overview]
Message-ID: <4C1BEF33.7090400@am.sony.com> (raw)
In-Reply-To: <20100616.005237.338122493954307067.imp@bsdimp.com>
On 06/15/10 23:52, M. Warner Losh wrote:
> In message: <4C187013.5000400@firmworks•com>
> Mitch Bradley <wmb@firmworks•com> writes:
> : Mike Rapoport wrote:
> : > Mitch Bradley wrote:
> : >> Mike Rapoport wrote:
> : >>> Mitch Bradley wrote:
> : >>>
> : >>>> The second topic is the hypothetical use of OFW as a HAL. That will
> : >>>> not happen for several reasons. The opposition to the idea is
> : >>>> widespread and deeply held, and there are good arguments to support
> : >>>> that opposition. Furthermore, the economic conditions necessary for
> : >>>> the creation of such a HAL do not exist in the ARM world, nor indeed
> : >>>> in the Linux world in general. (The necessary condition is the
> : >>>> ability for one company to impose a substantial change by fiat -
> : >>>> essentially a monopoly position.)
> : >>>>
> : >>>> Shall we agree, then, that any further discussion of the HAL issue is
> : >>>> "just for fun", and that nobody needs to feel threatened that it would
> : >>>> actually happen?
> : >>>
> : >>> I've recently worked with vendor versions of U-Boot for advanced ARM
> : >>> SoCs. There is already *huge* chunk of HAL code in those versions. And
> : >>> if there would be possibility to have callbacks into the firmware
> : >>> these chunks would only grow, IMHO.
> : >>
> : >> How can there be HAL code in U-Boot unless there is already the
> : >> possibility to have callbacks into the firmware?
> : >
> : > Currently it aims to abstract hardware from U-Boot and reuse the same
> : > HW access code across operating systems and bootloaders. If this code
> : > would have callbacks I afraid the things would became worse.
> :
> : The only way I can understand what you said is if I assume that by
> : "callback", you mean the following sequence:
> :
> : a) U-boot loads and executes the OS, providing to the OS the address
> : of some HW access routines that it can use
> : b) The OS calls one of those HW access routines
> : c) During the execution of that HW access routine, that routine calls
> : "back" into the OS, before returning. So a call into the OS is nested
> : inside a call into U-boot resident code.
> :
> : If that is what you are worried about, it is not what we were
> : discussing. We were discussing - and many people were against - step
> : (b).
> :
> : Are you saying that step (b) - the OS calling into routines provided
> : by U-Boot - is already the status quo?
>
> I don't know about status quo, but it certainly is supported. There's
> an option to allow for a secondary boot loader, such as FreeBSD's
> /boot/loader, to call back into uboot to read things from
> flash/disk/whatever, do network access, etc. Not so much a HAL, but
> more of an echo of the functionality provided by PC BIOS functions.
> /boot/loader can be viewed as a mini OS that calls back into uboot to
> have it do things. Once /boot/loader loads FreeBSD, btw, it and uboot
> disappear from the scene, so this isn't exactly a HAL situation...
Just for reference, there is a patch request on LKML to enable calling
openfirmware from the kernel on OLPC:
http://lkml.org/lkml/2010/6/18/336
-Frank
next prev parent reply other threads:[~2010-06-18 22:12 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AANLkTilK4YkRMJqlcRDOAlGBzpdlZuSo9NF5NrRNocHT@mail.gmail.com>
[not found] ` <33BD8E86-9397-432A-97BF-F154812C157B@digitaldans.com>
[not found] ` <AANLkTilv6TtPZs0DAwd8JlSV_J3VvMsvtVVOOeQauOIn@mail.gmail.com>
[not found] ` <4C13430B.5000907@firmworks.com>
[not found] ` <1276339529.1962.184.camel@pasglop>
[not found] ` <1276339684.1962.186.camel@pasglop>
[not found] ` <4C13B618.1030006@firmworks.com>
[not found] ` <1276383132.1962.195.camel@pasglop>
[not found] ` <AANLkTimRV8u3gDNCAIlROJoPcKs7jFwj2na3ZDFOg3O0@mail.gmail.com>
[not found] ` <4C146F18.9030008@firmworks.com>
2010-06-14 5:02 ` Request review of device tree documentation Grant Likely
2010-06-14 12:44 ` David Gibson
2010-06-14 14:59 ` Nicolas Pitre
2010-06-14 15:08 ` Grant Likely
2010-06-14 16:02 ` Jamie Lokier
2010-06-14 16:23 ` Nicolas Pitre
2010-06-14 16:29 ` Grant Likely
2010-06-14 16:28 ` Grant Likely
2010-06-14 16:33 ` Jamie Lokier
2010-06-14 16:58 ` Mitch Bradley
2010-06-14 17:26 ` Nicolas Pitre
2010-06-14 18:20 ` Mitch Bradley
2010-06-14 19:40 ` Nicolas Pitre
2010-06-14 20:08 ` Mark Brown
2010-06-16 6:09 ` Mike Rapoport
2010-06-16 6:13 ` Mitch Bradley
2010-06-16 6:17 ` Mike Rapoport
2010-06-16 6:32 ` Mitch Bradley
2010-06-16 6:47 ` Mike Rapoport
2010-06-16 7:40 ` Mitch Bradley
2010-06-16 9:45 ` Vladimir Pantelic
2010-06-16 10:39 ` Mike Rapoport
2010-06-16 11:41 ` Jamie Lokier
2010-06-16 13:48 ` Jamie Bennett
2010-06-16 14:39 ` Nicolas Pitre
2010-06-16 17:43 ` Tim Bird
2010-06-17 6:45 ` Benjamin Zores
2010-06-16 6:52 ` M. Warner Losh
2010-06-18 22:12 ` Frank Rowand [this message]
2010-06-15 2:02 ` David Gibson
2010-06-14 15:51 ` M. Warner Losh
[not found] ` <1276408773.1962.574.camel@pasglop>
2010-06-14 5:23 ` Grant Likely
2010-06-14 7:38 ` Russell King - ARM Linux
2010-06-14 7:45 ` Mitch Bradley
2010-06-14 9:25 ` Russell King - ARM Linux
2010-06-14 9:36 ` Benjamin Herrenschmidt
2010-06-14 9:47 ` Russell King - ARM Linux
2010-06-14 14:29 ` Jamie Lokier
2010-06-14 13:51 ` Nicolas Pitre
2010-06-14 15:35 ` Grant Likely
2010-06-14 15:58 ` Nicolas Pitre
2010-06-14 16:16 ` Grant Likely
[not found] ` <4C147EA5.3060500@firmworks.com>
[not found] ` <1276417792.1962.731.camel@pasglop>
2010-06-14 5:36 ` Grant Likely
2010-06-14 20:00 ` Ben Dooks
[not found] ` <1276408087.1962.552.camel@pasglop>
2010-06-14 5:13 ` Grant Likely
2010-06-14 6:09 ` Benjamin Herrenschmidt
2010-06-14 6:17 ` Mitch Bradley
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