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authorLv Zheng <lv.zheng@intel.com>2016-12-14 15:04:25 +0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-12-21 02:36:38 +0100
commit174cc7187e6f088942c8e74daa7baff7b44b33c9 (patch)
tree1e120c495fbee3aa883b697b2cc6c4d0c8734379 /drivers/acpi/acpica/actables.h
parent5a6e7ec3bfef2ea518061d8d5d77367952770efb (diff)
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ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel
ACPICA commit cac6790954d4d752a083e6122220b8a22febcd07 This patch back ports Linux acpi_get_table_with_size() and early_acpi_os_unmap_memory() into ACPICA upstream to reduce divergences. The 2 APIs are used by Linux as table management APIs for long time, it contains a hidden logic that during the early stage, the mapped tables should be unmapped before the early stage ends. During the early stage, tables are handled by the following sequence: acpi_get_table_with_size(); parse the table early_acpi_os_unmap_memory(); During the late stage, tables are handled by the following sequence: acpi_get_table(); parse the table Linux uses acpi_gbl_permanent_mmap to distinguish the early stage and the late stage. The reasoning of introducing acpi_get_table_with_size() is: ACPICA will remember the early mapped pointer in acpi_get_table() and Linux isn't able to prevent ACPICA from using the wrong early mapped pointer during the late stage as there is no API provided from ACPICA to be an inverse of acpi_get_table() to forget the early mapped pointer. But how ACPICA can work with the early/late stage requirement? Inside of ACPICA, tables are ensured to be remained in "INSTALLED" state during the early stage, and they are carefully not transitioned to "VALIDATED" state until the late stage. So the same logic is in fact implemented inside of ACPICA in a different way. The gap is only that the feature is not provided to the OSPMs in an accessible external API style. It then is possible to fix the gap by providing an inverse of acpi_get_table() from ACPICA, so that the two Linux sequences can be combined: acpi_get_table(); parse the table acpi_put_table(); In order to work easier with the current Linux code, acpi_get_table() and acpi_put_table() is implemented in a usage counting based style: 1. When the usage count of the table is increased from 0 to 1, table is mapped and .Pointer is set with the mapping address (VALIDATED); 2. When the usage count of the table is decreased from 1 to 0, .Pointer is unset and the mapping address is unmapped (INVALIDATED). So that we can deploy the new APIs to Linux with minimal effort by just invoking acpi_get_table() in acpi_get_table_with_size() and invoking acpi_put_table() in early_acpi_os_unmap_memory(). Lv Zheng. Link: https://github.com/acpica/acpica/commit/cac67909 Signed-off-by: Lv Zheng <lv.zheng@intel.com> Signed-off-by: Bob Moore <robert.moore@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/acpica/actables.h')
-rw-r--r--drivers/acpi/acpica/actables.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/acpi/acpica/actables.h b/drivers/acpi/acpica/actables.h
index 7dd527f8ca1d..94be8a8e6c08 100644
--- a/drivers/acpi/acpica/actables.h
+++ b/drivers/acpi/acpica/actables.h
@@ -166,6 +166,12 @@ acpi_tb_install_table_with_override(struct acpi_table_desc *new_table_desc,
acpi_status acpi_tb_parse_root_table(acpi_physical_address rsdp_address);
+acpi_status
+acpi_tb_get_table(struct acpi_table_desc *table_desc,
+ struct acpi_table_header **out_table);
+
+void acpi_tb_put_table(struct acpi_table_desc *table_desc);
+
/*
* tbxfload
*/