Re: [ros-dev] Merging our x86 HALs

[Hermès BÉLUSCA-MAÏTO]

Also, there is (at least parts of) HKLM\HARDWARE tree that is built at installation time
from info obtained from the HAL that is suitable for your platform, and that will be used
for the rest of the life of your Windows/ReactOS/... installation. So if you then think
that you'll be able to use "the same ReactOS installation [...] on several
different x86 computers" (to quote you), it'll be a bit more complicated than
that!!!!

Besides this, I've a question about your observation that in the APIC hal (not ACPI)
there's different implementation of HalpCalibrateStallExecution and HalpInitializePICs
/ HalpInitializeLegacyPIC . Isn't it precisely because these stuff are completely
different from the standard PICs used in platforms for which the standard HAL (and
possibly the ACPI HAL) are used?

For your x2APIC question, if this shares a good stuff wrt. APIC, then either it would be
inside the same APIC HAL, otherwise there could be two HALs, APIC and the other one, but
made from common "generic" code + different code that depend on the APIC vs.
x2APIC.

>   The user is also able to select a custom HAL during
> setup, even if it wouldn't work on the machine. We should give neither the user nor
> the setup the ability to decide. The HAL itself knows best at boot-up what features to
> enable and what not. 
Actually we should, because the detection might not work (of course in our simple case
"ACPI UP/MP" vs. "Standard", it's simple, but think about other
platforms where there can be subtle differences), AND the fact that an advanced user may
want to specify one's HAL. And normally it's not the setup that decides about the
HAL, but the bootloader. The bootloader (ntldr / winldr) also has the capability of
detecting the HAL to use and load, unless being specified otherwise by a switch in the
command-lines in boot.ini (ntldr) or somewhere in the BCD (bootmgr/winldr).

H.

>   -----Message d'origine-----
>  De : Ros-dev [mailto:[e-mail]] De la part de Hermès
>  BÉLUSCA-MAÏTO
>  Envoyé : lundi 11 décembre 2017 01:18
>  À : 'ReactOS Development List'
>  Objet : Re: [ros-dev] Merging our x86 HALs
>  
>  I personally think it's a bit "against" the philosophy of HALs, namely
> having a
>  lightweight hardware abstraction layer code for different platforms.
>  If you basically put all the HALs into one, then you obtain bloated stuff (which
>  remains in memory for the whole life of the OS). Example: standard HAL is
>  1MB vs. ACPI HAL which is few kB.
>  A bit more work and you could even get a monolithic kernel! Nah joking xD ...
>  but not completely.
>  
>  Note that if Windows nowadays has only one hal, it's because they now support
>  basically only one "architecture"/platform, namely, ACPI multiprocessor (to
> put
>  it simple). It has its pros, but also a lot of cons.
>  
>  To solve the original problem you have encountered in our code, just introduce
>  common/generic .c files containing the code that is similar everywhere, even
>  at the level of all the hals, or at the level of (let's say) a given CPU
> "type" (x86,
>  x64...), then there are the other .c that implement the different flavours of the
>  procedures that depend on the specific arch/platform.
>  
>  Like this:
>  
>  HALs
>  +---- Generic code
>  +---- HAL for a given arch #1 (e.g. x86)
>  |     +---- Generic code for this arch
>  |     +---- Code for standard (non-ACPI) HAL
>  |     +---- Code for ACPI HAL
>  |     +---- Code for a different HAL flavour (platform)?
>  |     +---- ...
>  |
>  +---- HAL for arch #2
>  |     +---- Generic code
>  |     +---- Code for platform
>  |     +---- Code for second platform
>  |     +---- ...
>  |
>  +---- etc...
>  
>  This is very clear and maintainable.
>  
>  H.
>  
> >   -----Message d'origine-----
> >  De : Ros-dev [mailto:[e-mail]] De la part de Colin
> >  Finck Envoyé : dimanche 10 décembre 2017 19:55 À : ros-dev(a)reactos.org
> >  Objet : Re: [ros-dev] Merging our x86 HALs
> >
> >  Am 10.12.2017 um 19:38 schrieb David Quintana (gigaherz):
> > >   Colin: Are we talking merge and decide which
> > > method to use at
> > >  runtime 
> >  Exactly! We don't even need boot flags: Just like the setup currently
> >  detects an ACPI-compliant computer, the HAL could do this at boot-up.
> >  It's also not too hard to detect the presence of an APIC.
> >
> >  I think a universal HAL for every x86 machine wouldn't be noticeably
> >  larger than an ACPI+SMP HAL.
> >
> >
> >  - Colin
> >
> >  _______________________________________________
> >  Ros-dev mailing list
> >  Ros-dev(a)reactos.org
> >  http://www.reactos.org/mailman/listinfo/ros-dev 
>  
>  
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