Re: [PATCH v1 3/8] ACPI: bus: Split _OSC evaluation out of acpi_run_osc()

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Thu, 18 Dec 2025 21:36:08 +0100
"Rafael J. Wysocki" <rafael@kernel.org> wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Split a function for evaluating _OSL called acpi_eval_osc() out of

_OSC

> acpi_run_osc() to facilitate subsequent changes and add some more
> parameters sanity checks to the latter.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

One comment on the fun static keyword usage.  Next time I have
to ask/answer some silly C questions in an interview that one is definitely going
in :)
> ---
>  drivers/acpi/bus.c |   89 ++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 52 insertions(+), 37 deletions(-)
> 
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -195,52 +195,67 @@ static void acpi_dump_osc_data(acpi_hand
>  			 OSC_INVALID_REVISION_ERROR | \
>  			 OSC_CAPABILITIES_MASK_ERROR)
>  
> -acpi_status acpi_run_osc(acpi_handle handle, struct acpi_osc_context *context)
> +static int acpi_eval_osc(acpi_handle handle, guid_t *guid, int rev,
> +			 struct acpi_buffer *cap,
> +			 union acpi_object in_params[static 4],

This static usage has such non intuitive behavior maybe use
the new at_least marking in compiler_types.h to indicate
what protection against wrong sizes it can offer.

> +			 struct acpi_buffer *output)
>  {
> -	acpi_status status;
>  	struct acpi_object_list input;
> -	union acpi_object in_params[4];
>  	union acpi_object *out_obj;
> +	acpi_status status;
> +
> +	in_params[0].type = ACPI_TYPE_BUFFER;
> +	in_params[0].buffer.length = sizeof(*guid);
> +	in_params[0].buffer.pointer = (u8 *)guid;
> +	in_params[1].type = ACPI_TYPE_INTEGER;
> +	in_params[1].integer.value = rev;
> +	in_params[2].type = ACPI_TYPE_INTEGER;
> +	in_params[2].integer.value = cap->length / sizeof(u32);
> +	in_params[3].type = ACPI_TYPE_BUFFER;
> +	in_params[3].buffer.length = cap->length;
> +	in_params[3].buffer.pointer = cap->pointer;
> +	input.pointer = in_params;
> +	input.count = 4;
> +
> +	output->length = ACPI_ALLOCATE_BUFFER;
> +	output->pointer = NULL;
> +
> +	status = acpi_evaluate_object(handle, "_OSC", &input, output);
> +	if (ACPI_FAILURE(status) || !output->length)
> +		return -ENODATA;
> +
> +	out_obj = output->pointer;
> +	if (out_obj->type != ACPI_TYPE_BUFFER ||
> +	    out_obj->buffer.length != cap->length) {
> +		acpi_handle_debug(handle, "Invalid _OSC return buffer\n");
> +		acpi_dump_osc_data(handle, guid, rev, cap);
> +		ACPI_FREE(out_obj);
> +		return -ENODATA;
> +	}
> +
> +	return 0;
> +}