Re: [Xen-devel] [PATCH 6/9] Add cpu idle pwr mgmt to xen

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> "Wei, Gang" <gang.wei@xxxxxxxxx> 25.04.08 07:08 >>>
>Port acpi bit register support from Linux.
>
>Bit register read/write is required by deep C code.
>Remove dependendy on acpi_sinfo.
>
>Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
>
>+static void __init
>+acpi_fadt_parse_reg(struct acpi_table_fadt *fadt)
>+{
>+      memcpy(&acpi_gbl_FADT, fadt, sizeof(acpi_gbl_FADT));
>+
>+      memcpy(&acpi_gbl_xpm1a_enable, &(fadt->xpm1a_event_block),
>+              sizeof(acpi_gbl_xpm1a_enable));
>+      memcpy(&acpi_gbl_xpm1b_enable, &(fadt->xpm1b_event_block),
>+              sizeof(acpi_gbl_xpm1b_enable));
>+
>+      acpi_gbl_xpm1a_enable.address += 2;
>+      acpi_gbl_xpm1b_enable.address += 2;
>+}

This doesn't look right: For one, PM1b is optional, and hence if you add
a non-zero value to a zero address (which is commonly used as the
presence indicator) consumers all of the sudden could consider the block
present. The other thing is that while on today's systems using a literal
2 here may be correct, it isn't according to the ACPI spec - you'd ought
to add half the block width instead.

Jan


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