Date: Thu, 23 Jul 2009 08:08:35 +0200 From: Andre Albsmeier <Andre.Albsmeier@siemens.com> To: Doug Ambrisko <ambrisko@ambrisko.com> Cc: freebsd-hackers@freebsd.org, Andre Albsmeier <Andre.Albsmeier@siemens.com> Subject: Re: Reading acpi memory from a driver attached to hostb Message-ID: <20090723060835.GB62628@curry.mchp.siemens.de> In-Reply-To: <200907221648.n6MGmu58035040@ambrisko.com> References: <20090718133938.GA7802@curry.mchp.siemens.de> <200907221648.n6MGmu58035040@ambrisko.com>
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On Wed, 22-Jul-2009 at 09:48:56 -0700, Doug Ambrisko wrote:
> Andre Albsmeier writes:
> | On Sat, 18-Jul-2009 at 10:25:06 +0100, Rui Paulo wrote:
> | > On 18 Jul 2009, at 09:10, Andre Albsmeier wrote:
> | >
> | > > On Fri, 17-Jul-2009 at 12:53:53 -0700, Julian Elischer wrote:
> | > >> Andre Albsmeier wrote:
> | > >>> [CC'ing this to Rui Paulo since he tried to help me a while ago]
> | > >>>
> | > >>> Since my driver is a child of hostb0, I have no idea of how to
> | > >>> access
> | > >>> acpi0's memory area. Here is a devinfo -r to make things clear:
> | > >>>
> | > >> ...
> | > >>>
> | > >>> Earlier, I was given the hint to attach as a child of acpi (see the
> | > >>> old mail attached below) but in this case I didn't have access to
> | > >>> the
> | > >>> hostb registers which I need as well.
> | > >>>
> | > >>> The only thing I see is: Attach two drivers -- one as child of acpi
> | > >>> and another as child of hostb and let them communicate somehow (no
> | > >>> idea how to do this).
> | > >>>
> | > >>> I have also done crazy things like searching for acpi0 and trying
> | > >>> to bus_alloc_resource() the memory I am interested in but this also
> | > >>> failed.
> | > >>>
> | > >>> Or is it possible to free(!) somehow the address space from acpi0
> | > >>> and pass it to hostb0 so I can bus_alloc_resource() it?
> | > >>>
> | > >>
> | > >> You can probably make two drivers in one which cooperate to
> | > >> allow access to both sets of resources.
> | > >
> | > > Hmm, that's what I meant by: Attach two drivers -- one as child of
> | > > acpi
> | > > and another as child of hostb...
> | > >
> | > > And that's similar to Rui Paulo's suggestion a while ago:
> | > >
> | > >> You'll probably need to create a fake ACPI child driver to access it.
> | > >>
> | > >> Create your identify routine with something like:
> | > >>
> | > >> static void mydriver_identify(driver_t *driver, device_t parent)
> | > >> {
> | > >> if (device_find_child(parent, "mydriver", -1) == NULL &&
> | > >> mydriver_match(parent))
> | > >> device_add_child(parent, "mydriver", -1);
> | > >> }
> | > >>
> | > >> mydriver_match() should check if you were given the acpi0 device.
> | > >
> | > > But in order to attach to acpi0, I need to say
> | > >
> | > > DRIVER_MODULE( eccmon, acpi, eccmon_driver, eccmon_devclass, NULL,
> | > > NULL );
> | > >
> | > > instead of
> | > >
> | > > DRIVER_MODULE( eccmon, hostb, eccmon_driver, eccmon_devclass, NULL,
> | > > NULL );
> | > >
> | > > This way I could attach to acpi but not to hostb anymore....
> | > >
> | > > I have searched the net for solutions, I have read newbus-draft.txt
> | > > and newbus-intro.txt and Warner Losh's newbus-led.c (thanks to all
> | > > of these my driver is working on other mainboards where it doesn't
> | > > have to access foreign memory) but didn't find anything.
> | >
> | > I'm out of ideas.
> | > John, do you know if this is a newbus limitation or if it can be
> | > worked around ?
> |
> | I assume it is possible somehow, I am just too stupid (it is the first
> | driver I wrote). John, for easy reference, here is my initial message:
> |
> | http://lists.freebsd.org/pipermail/freebsd-hackers/2009-July/029127.html
> |
> | Please remember all, that I need the access to the acpi0 memory location
> | only for a few reads during probing/attaching, not later.
> |
> | I have also read somewhere that, when resources are allocated, the
> | system "walks up" the device tree until it finds the resource. Since
> | my driver is below hostb0 and hostb0 is below acpi0 I thought it
> | should work but it doesn't..
>
> FWIW, you might look at ipmi(4) especially in some early states since
> it can probe and attach in many ways (isa, acpi, pci etc.) and had to
> figure out the best way to attach. Also it had various front ends.
> If I recall correctly, I did a find for a driver (ie. acpi) then
> select the first instance. Once you get that handle then you can
> request device resources from it, get the info you need then release
> that stuff. However, you won't get the module auto-loading part
> that you would get if you created a module that depended on both.
> That might get you enough of a hint. Also there are some generic
> stuff to read various memory bits like SMBIOS areas etc. This is
> used in ipmi(4) as well since the attachment can be defined in SMBIOS.
> If you have a specific question, about why the driver did something
> I should recall that. The ipmi(4) driver is in fairly clean. There
> is some improvements I still need to do on probe/attachment that
> causes a bogus ipmi1 at times.
Thanks a lot for this interesting information. I see, things are more
complicated than I thought. There is no easy way having a quick glance
at "foreign" memory during probing. Now I have to figure out how to get
the order of probing/attaching done. One thing I could do is:
1. attach mydriver_ACPI to acpi0
2. probe mydriver under hostb0, check if we need access to
sysresources from acpi0 (depends on the chipset found).
If no, goto 5.
3. ask mydriver_ACPI about stuff I want to know (HOW?)
4. tell mydriver to detach from acpi0 (HOW?)
5. attach mydriver to hostb0 and do my work
What I would like more is something like:
1. probe mydriver under hostb0, check if we need access to
sysresources from acpi0 (depends on the chipset found).
If no, goto 3.
2. ask mydriver_ACPI to attach to acpi0, give me the info
I want, detach mydriver_ACPI (HOW?)
3. attach mydriver to hostb0 and do my work
Thanks,
-Andre
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