On Tuesday, September 09, 2014 04:57:58 PM Mark Salter wrote:
> ACPI 5.1 adds a _CCA object to indicate memory coherency
> of a bus master device. It is an integer with zero meaning
> non-coherent and one meaning coherent. This attribute may
> be inherited from a parent device. It may also be missing
> entirely, in which case, an architecture-specific default
> is assumed.
>
> This patch adds a utility function to parse a device handle
> (and its parents) for a _CCA object and return the coherency
> attribute if found.
>
> Signed-off-by: Mark Salter <msalter@xxxxxxxxxx>
> ---
> drivers/acpi/utils.c | 26 ++++++++++++++++++++++++++
> include/acpi/acpi_bus.h | 2 ++
> 2 files changed, 28 insertions(+)
>
> diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
> index 07c8c5a..aec9656 100644
> --- a/drivers/acpi/utils.c
> +++ b/drivers/acpi/utils.c
> @@ -698,3 +698,29 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, int rev, u64 funcs)
> return false;
> }
> EXPORT_SYMBOL(acpi_check_dsm);
> +
> +/**
> + * acpi_check_coherency - check for memory coherency of a device
> + * @handle: ACPI device handle
> + * @val: Pointer to returned value
> + *
> + * Search a device and its parents for a _CCA method and return
> + * its value.
> + */
> +acpi_status acpi_check_coherency(acpi_handle handle, int *val)
> +{
> + unsigned long long data;
> + acpi_status status;
> +
> + do {
> + status = acpi_evaluate_integer(handle, "_CCA", NULL, &data);
> + if (!ACPI_FAILURE(status)) {
We have an ACPI_SUCCESS() macro for that.
> + *val = data;
> + break;
> + }
> + status = acpi_get_parent(handle, &handle);
> + } while (!ACPI_FAILURE(status));
> +
And here.
Anyway, how do you think this routine will be used? Do you have any
particular use cases in mind?
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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