[PATCH 4/6] acpi: fix compilation for 32-bit

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Build test on x86 fails due to pointer cast and because of forcing the
bigger alignment on the flexible array.

The problematic pointer cast is for the XSDT, which is 64-bit-only, so
let's fix the cast and return an error if we somehow see an XSDT on
32-bit.

For the flexible array, the first struct member is already packed, so we
should arrive at the same result by just dropping the packed from the
second member, so they get normal alignment.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/bus/acpi.c | 6 ++++--
 include/acpi.h     | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/bus/acpi.c b/drivers/bus/acpi.c
index 593617073345..61178db0c8db 100644
--- a/drivers/bus/acpi.c
+++ b/drivers/bus/acpi.c
@@ -174,10 +174,12 @@ static int acpi_register_devices(struct bus_type *bus)
 		sig = "RSDT";
 		root = (struct acpi_rsdt *)(unsigned long)rsdp->rsdt_addr;
 		entry_count = (root->sdt.len - sizeof(struct acpi_rsdt)) / sizeof(u32);
-	} else {
+	} else if (sizeof(void *) == 8) {
 		sig = "XSDT";
-		root = (struct acpi_rsdt *)((struct acpi2_rsdp *)rsdp)->xsdt_addr;
+		root = (struct acpi_rsdt *)(uintptr_t)((struct acpi2_rsdp *)rsdp)->xsdt_addr;
 		entry_count = (root->sdt.len - sizeof(struct acpi_rsdt)) / sizeof(u64);
+	} else {
+		return -EIO;
 	}
 
 	if (acpi_sigcmp(sig, root->sdt.signature)) {
diff --git a/include/acpi.h b/include/acpi.h
index 0756f94501cc..837476424664 100644
--- a/include/acpi.h
+++ b/include/acpi.h
@@ -113,9 +113,9 @@ struct __packed acpi_sdt { /* system description table header */
 	u32		creator_revision;
 };
 
-struct __packed acpi_rsdt { /* system description table header */
+struct acpi_rsdt { /* system description table header */
 	struct acpi_sdt	sdt;
-	struct acpi_sdt	* __aligned(8) entries[];
+	struct acpi_sdt	*entries[];
 };
 
 struct acpi_driver {
-- 
2.39.2