Hi Rafael，
Could you please give your comments on this patch? Thanks in advanced!
On 2016/4/7 20:03, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
>
> ACPI 6.0 introduces a new table STAO to list the devices which are used
> by Xen and can't be used by Dom0. On Xen virtual platforms, the physical
> UART is used by Xen. So here it hides UART from Dom0.
>
> CC: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> (supporter:ACPI)
> CC: Len Brown <lenb@xxxxxxxxxx> (supporter:ACPI)
> CC: linux-acpi@xxxxxxxxxxxxxxx (open list:ACPI)
> Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> ---
> drivers/acpi/scan.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 74 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 5f28cf7..cfc73fe 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -46,6 +46,13 @@ DEFINE_MUTEX(acpi_device_lock);
> LIST_HEAD(acpi_wakeup_device_list);
> static DEFINE_MUTEX(acpi_hp_context_lock);
>
> +/*
> + * The UART device described by the SPCR table is the only object which needs
> + * special-casing. Everything else is covered by ACPI namespace paths in STAO
> + * table.
> + */
> +static u64 spcr_uart_addr;
> +
> struct acpi_dep_data {
> struct list_head node;
> acpi_handle master;
> @@ -1453,6 +1460,41 @@ static int acpi_add_single_object(struct acpi_device **child,
> return 0;
> }
>
> +static acpi_status acpi_get_resource_memory(struct acpi_resource *ares,
> + void *context)
> +{
> + struct resource *res = context;
> +
> + if (acpi_dev_resource_memory(ares, res))
> + return AE_CTRL_TERMINATE;
> +
> + return AE_OK;
> +}
> +
> +static bool acpi_device_should_be_hidden(acpi_handle handle)
> +{
> + acpi_status status;
> + struct resource res;
> +
> + /* Check if it should ignore the UART device */
> + if (!(spcr_uart_addr && acpi_has_method(handle, METHOD_NAME__CRS)))
> + return false;
> +
> + /*
> + * The UART device described in SPCR table is assumed to have only one
> + * memory resource present. So we only look for the first one here.
> + */
> + status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> + acpi_get_resource_memory, &res);
> + if (ACPI_FAILURE(status) || res.start != spcr_uart_addr)
> + return false;
> +
> + acpi_handle_info(handle, "The UART device @%pa in SPCR table will be hidden\n",
> + &res.start);
> +
> + return true;
> +}
> +
> static int acpi_bus_type_and_status(acpi_handle handle, int *type,
> unsigned long long *sta)
> {
> @@ -1466,6 +1508,9 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type,
> switch (acpi_type) {
> case ACPI_TYPE_ANY: /* for ACPI_ROOT_OBJECT */
> case ACPI_TYPE_DEVICE:
> + if (acpi_device_should_be_hidden(handle))
> + return -ENODEV;
> +
> *type = ACPI_BUS_TYPE_DEVICE;
> status = acpi_bus_get_status_handle(handle, sta);
> if (ACPI_FAILURE(status))
> @@ -1916,9 +1961,24 @@ static int acpi_bus_scan_fixed(void)
> return result < 0 ? result : 0;
> }
>
> +static void __init acpi_get_spcr_uart_addr(void)
> +{
> + acpi_status status;
> + struct acpi_table_spcr *spcr_ptr;
> +
> + status = acpi_get_table(ACPI_SIG_SPCR, 0,
> + (struct acpi_table_header **)&spcr_ptr);
> + if (ACPI_SUCCESS(status))
> + spcr_uart_addr = spcr_ptr->serial_port.address;
> + else
> + printk(KERN_WARNING PREFIX "STAO table present, but SPCR is missing\n");
> +}
> +
> int __init acpi_scan_init(void)
> {
> int result;
> + acpi_status status;
> + struct acpi_table_stao *stao_ptr;
>
> acpi_pci_root_init();
> acpi_pci_link_init();
> @@ -1934,6 +1994,20 @@ int __init acpi_scan_init(void)
>
> acpi_scan_add_handler(&generic_device_handler);
>
> + /*
> + * If there is STAO table, check whether it needs to ignore the UART
> + * device in SPCR table.
> + */
> + status = acpi_get_table(ACPI_SIG_STAO, 0,
> + (struct acpi_table_header **)&stao_ptr);
> + if (ACPI_SUCCESS(status)) {
> + if (stao_ptr->header.length > sizeof(struct acpi_table_stao))
> + printk(KERN_INFO PREFIX "STAO Name List not yet supported.");
> +
> + if (stao_ptr->ignore_uart)
> + acpi_get_spcr_uart_addr();
> + }
> +
> mutex_lock(&acpi_scan_lock);
> /*
> * Enumerate devices in the ACPI namespace.
>
--
Shannon
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