MADT PCAT_COMPAT flag values reversed?

[Jnosh]

In source/include/actbl1.h, ACPI_TABLE_MADT includes a flag field.

The preprocessor define ACPI_MADT_PCAT_COMPAT specifies a mask for the PCAT_COMPAT flag while ACPI_MADT_DUAL_PIC and ACPI_MADT_MULTIPLE_APIC specify the values of said flag.

My interpretation of said defines is that ACPI_MADT_DUAL_PIC indicates the presence of dual 8259 PICs, whereas ACPI_MADT_MULTIPLE_APIC indicates their absence.

i.e. hasDualPics = (madt->Flags & ACPI_MADT_PCAT_COMPAT) == ACPI_MADT_DUAL_PIC

However, ACPI_MADT_DUAL_PIC is defined as 0 while the ACPI specification says regarding the PCAT_COMPAT flag:

A one indicates that the system also has a PC-AT-compatible dual-8259 setup.
(ACPI 6.1, Table 5-45 Multiple APIC Flags, p. 144)

I am probably misunderstanding or misreading something but I would appreciate any insight.

[acpibob]

Looks like you might be right From: Janosch Hildebrand [mailto:notifications@github.com] Sent: Tuesday, March 7, 2017 11:58 AM To: acpica/acpica <acpica@noreply.github.com> Cc: Subscribed <subscribed@noreply.github.com> Subject: [acpica/acpica] MADT PCAT_COMPAT flag values reversed? (#224) In source/include/actbl1.h, ACPI_TABLE_MADT includes a flag field. The preprocessor define ACPI_MADT_PCAT_COMPAT specifies a mask for the PCAT_COMPAT flag while ACPI_MADT_DUAL_PIC and ACPI_MADT_MULTIPLE_APIC specify the values of said flag. My interpretation of said defines is that ACPI_MADT_DUAL_PIC indicates the presence of dual 8259 PICs, whereas ACPI_MADT_MULTIPLE_APIC indicates their absence. i.e. hasDualPics = (madt->Flags & ACPI_MADT_PCAT_COMPAT) == ACPI_MADT_DUAL_PIC However, ACPI_MADT_DUAL_PIC is defined as 0 while the ACPI specification says regarding the PCAT_COMPAT flag: A one indicates that the system also has a PC-AT-compatible dual-8259 setup. (ACPI 6.1, Table 5-45 Multiple APIC Flags, p. 144) I am probably misunderstanding or misreading something but I would appreciate any insight. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub<#224>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AA6_rEkDH3g2RSdJVNh_c1F9pr3S-Swfks5rjbbbgaJpZM4MV88O>.

[Jnosh]

Thanks. I am currently running on Qemu, Bochs and Virtualbox, all of which emulate the PICs and they report 1 as the value of that flag in their MADTs. I was worried I might be misunderstanding how to use the defined constants.

I added a pull request to fix this, if that is OK: #225

I hope this doesn't cause any compatibility issues but since no-one noticed that before, those definitions probably aren't in broad use?
I did some quick googling and only found the definitions in the ACPICA header in various OSS projects but no actual uses.