[Xen-devel] [PATCH v6 10/22] acpi/table: Introduce acpi_table_get_entry_madt to get specified entry

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>

This function could get the specified index entry of MADT table. This
would be useful when it needs to get the contens of the entry.

Cc: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
---
V6: address Jan's comments
---
 xen/drivers/acpi/tables.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/acpi.h    |  2 ++
 2 files changed, 61 insertions(+)

diff --git a/xen/drivers/acpi/tables.c b/xen/drivers/acpi/tables.c
index f81c369..1d15d3a 100644
--- a/xen/drivers/acpi/tables.c
+++ b/xen/drivers/acpi/tables.c
@@ -221,6 +221,65 @@ void __init acpi_table_print_madt_entry(struct 
acpi_subtable_header *header)
        }
 }
 
+static struct acpi_subtable_header * __init
+acpi_get_entry(const char *id, unsigned long table_size,
+              const struct acpi_table_header *table_header,
+              enum acpi_madt_type entry_id, unsigned int entry_index)
+{
+       struct acpi_subtable_header *entry;
+       int count = 0;
+       unsigned long table_end;
+
+       if (!table_size)
+               return NULL;
+
+       if (!table_header) {
+               printk(KERN_WARNING PREFIX "%4.4s not present\n", id);
+               return NULL;
+       }
+
+       table_end = (unsigned long)table_header + table_header->length;
+
+       /* Parse all entries looking for a match. */
+       entry = (void *)table_header + table_size;
+
+       while ((unsigned long)(entry + 1) < table_end) {
+               if (entry->length < sizeof(*entry)) {
+                       printk(KERN_ERR PREFIX "[%4.4s:%#x] Invalid length\n",
+                              id, entry_id);
+                       return NULL;
+               }
+
+               if (entry->type == entry_id) {
+                       if (count == entry_index)
+                               return entry;
+                       count++;
+               }
+
+               entry = (void *)entry + entry->length;
+       }
+
+       return NULL;
+}
+
+struct acpi_subtable_header * __init
+acpi_table_get_entry_madt(enum acpi_madt_type entry_id,
+                         unsigned int entry_index)
+{
+       struct acpi_table_header *table_header;
+       acpi_status status;
+
+       status = acpi_get_table(ACPI_SIG_MADT, acpi_apic_instance,
+                               &table_header);
+       if (ACPI_FAILURE(status)) {
+               printk(KERN_WARNING PREFIX "%4.4s not present\n",
+                      ACPI_SIG_MADT);
+               return NULL;
+       }
+
+       return acpi_get_entry(ACPI_SIG_MADT, sizeof(struct acpi_table_madt),
+                             table_header, entry_id, entry_index);
+}
 
 int __init
 acpi_parse_entries(char *id, unsigned long table_size,
diff --git a/xen/include/xen/acpi.h b/xen/include/xen/acpi.h
index f05b160..946877f 100644
--- a/xen/include/xen/acpi.h
+++ b/xen/include/xen/acpi.h
@@ -79,6 +79,8 @@ int acpi_parse_entries(char *id, unsigned long table_size,
                       int entry_id, unsigned int max_entries);
 int acpi_table_parse_entries(char *id, unsigned long table_size,
        int entry_id, acpi_table_entry_handler handler, unsigned int 
max_entries);
+struct acpi_subtable_header *acpi_table_get_entry_madt(enum acpi_madt_type id,
+                                                     unsigned int entry_index);
 int acpi_table_parse_madt(enum acpi_madt_type id, acpi_table_entry_handler 
handler, unsigned int max_entries);
 int acpi_table_parse_srat(int id, acpi_madt_entry_handler handler,
        unsigned int max_entries);
-- 
2.0.4



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