On Thu, Mar 31, 2016 at 1:23 PM, Shannon Zhao <zhaoshenglong@xxxxxxxxxx> 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 | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 69 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 5f28cf7..29f26fc 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -45,6 +45,7 @@ static LIST_HEAD(acpi_scan_handlers_list);
> DEFINE_MUTEX(acpi_device_lock);
> LIST_HEAD(acpi_wakeup_device_list);
> static DEFINE_MUTEX(acpi_hp_context_lock);
> +static u64 spcr_uart_addr;
>
> struct acpi_dep_data {
> struct list_head node;
> @@ -1453,6 +1454,42 @@ 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 != 0) {
Why not to write this as
if (spcr_uart_addr) {
Or even
if (!spcr_uart_addr)
return false;
and then the indentation level of the rest will be reduced.
> + if (!acpi_has_method(handle, METHOD_NAME__CRS))
> + return false;
> +
I'd like to see a comment here that the devices in question are
assumed to have only one memory resource present which is why we only
look for the first one.
> + status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> + acpi_get_resource_memory, &res);
> + if (ACPI_FAILURE(status))
> + return false;
> +
> + if (res.start == spcr_uart_addr) {
> + printk(KERN_INFO PREFIX "The UART device @%pa in SPCR table will be hidden\n",
> + &res.start);
> + return true;
> + }
> + }
> +
> + return false;
> +}
> +
Thanks,
Rafael
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