linux-kernel - Re: [PATCH] tpm_crb: Use the common ACPI definition of struct acpi

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Date:	Sun, 6 Dec 2015 03:25:11 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tpm_crb: Use the common ACPI definition of struct
 acpi_tpm2

On Thu, Dec 03, 2015 at 10:02:17AM -0700, Jason Gunthorpe wrote:
> On Thu, Dec 03, 2015 at 10:27:53AM +0200, Jarkko Sakkinen wrote:
> > On Wed, Dec 02, 2015 at 12:19:00PM -0700, Jason Gunthorpe wrote:
> > > include/acpi/actbl2.h is the proper place for these definitions
> > > and the needed TPM2 ones have been there since
> > > commit 413d4a6defe0 ("ACPICA: Update TPM2 ACPI table")
> > > 
> > > This also drops the le32_to_cpu for members of this table,
> > > consistent with other ACPI stuff.
> > 
> > Why le32_to_cpu() is not needed?
> 
> Why is it needed?
> 
> None of the fields are marked le32 in the struct and no other ACPI
> thing I could find swaps.
> 
> If swapping is needed then the struct fields must be declared as 'le'

I'm just puzzling with three things:

1. Does it do conversion to the CPU format internally if you use the
   tables in a big-endian environment?
2. Isn't that code import from ACPICA? That would explains why it does
   not have tagged fields.
3. Could the reason be for such conversions not widely applied in the
   kernel that ACPI has been previously mostly used only in the PC/x86
   ecosystem?

AFAIK ACPI exist also for ARM64 servers, which can be a big-endian
environment.

> Jason

/Jarkko
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