Re: PROBLEM: Calling ObjectType on buffer field reports type integer

[Maximilian Luz <luzmaximilian@gmail.com>]

On 12/3/19 11:21 PM, Kaneda, Erik wrote:
> Hi Maximilian,
> 
> Please try the patch below:

Hi,

I've tested this on 5.4.1 and the current upstream master now.
Unfortunately it doesn't seem to fix the issue.

Specifically, it seems like the flag doesn't get set here
(printk-debugging indicates that the code in the if never runs):

>   /******************************************************************************
> diff -Nurp linux.before_name/drivers/acpi/acpica/dsutils.c linux.after_name/drivers/acpi/acpica/dsutils.c
> --- linux.before_name/drivers/acpi/acpica/dsutils.c	2019-12-03 13:36:21.782578718 -0800
> +++ linux.after_name/drivers/acpi/acpica/dsutils.c	2019-12-03 13:36:17.765579110 -0800
> @@ -470,6 +470,9 @@ acpi_ds_create_operand(struct acpi_walk_
>   			    ACPI_CAST_PTR(union acpi_operand_object,
>   					  walk_state->deferred_node);
>   			status = AE_OK;
> +			if (walk_state->opcode == AML_CREATE_FIELD_OP) {
> +				obj_desc->buffer_field.is_create_field = TRUE;
> +			}
>   		} else {	/* All other opcodes */
> 
>   			/*

That of course means that the if condition here is still not fulfilled,
so the problem is not fixed.

> diff -Nurp linux.before_name/drivers/acpi/acpica/exfield.c linux.after_name/drivers/acpi/acpica/exfield.c
> --- linux.before_name/drivers/acpi/acpica/exfield.c	2019-12-03 13:36:21.791578717 -0800
> +++ linux.after_name/drivers/acpi/acpica/exfield.c	2019-12-03 13:36:18.257579062 -0800
> @@ -153,12 +154,17 @@ acpi_ex_read_data_from_field(struct acpi
>   	 * the use of arithmetic operators on the returned value if the
>   	 * field size is equal or smaller than an Integer.
>   	 *
> +	 * However, all buffer fields created by create_field operator needs to
> +	 * remain as a buffer to match other AML interpreter implementations.
> +	 *
>   	 * Note: Field.length is in bits.
>   	 */
>   	buffer_length =
>   	    (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc->field.bit_length);
>   
> -	if (buffer_length > acpi_gbl_integer_byte_width) {
> +	if (buffer_length > acpi_gbl_integer_byte_width ||
> +	    (obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD &&
> +	     obj_desc->buffer_field.is_create_field)) {
>   
>   		/* Field is too large for an Integer, create a Buffer instead */
> 

If I'm not mistaken I've proposed a patch here that is conceptually
quite similar (but may have some flaws or cause other issues, as I'm not
really familiar with the ACPICA code-base). My idea was to modify
acpi_ds_init_buffer_field (dsopcode.c) instead of
acpi_ds_create_operand. As said, I'm not sure however if this may have
any other consequences that I'm unaware of.

Also I've avoided creating an is_create_field flag by changing the field
access from AML_FIELD_ACCESS_BYTE to AML_FIELD_ACCESS_BUFFER (which
doesn't seem to be used anywhere else) and checking that, but the
general idea of extending the if condition in
acpi_ex_read_data_from_field is the same.

Link to the patch:
https://github.com/qzed/linux-surfacegen5-acpi/blob/2014964bac52f138109443de3e92dc2c6cff5e83/patches/5.3/0001-ACPI-Fix-buffer-integer-type-mismatch.patch

Thanks,
Maximilian