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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html