From 7e148f2ed365c89f50701ed45acd6e36138de447 Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Tue, 7 Jul 2020 13:11:50 -0600 Subject: acpigen: Support writing a length It is convenient to write a length value for preceding a block of data. Of course the length is not known or is hard to calculate a priori. So add a way to mark the start on a stack, so the length can be updated when known. Signed-off-by: Simon Glass Reviewed-by: Wolfgang Wallner Reviewed-by: Bin Meng --- include/acpi/acpigen.h | 41 +++++++++++++++++++++++++++++++++++++++++ include/dm/acpi.h | 9 ++++++++- 2 files changed, 49 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/acpi/acpigen.h b/include/acpi/acpigen.h index 9c1faf7bf2b..18409b613c6 100644 --- a/include/acpi/acpigen.h +++ b/include/acpi/acpigen.h @@ -14,6 +14,9 @@ struct acpi_ctx; +/* Top 4 bits of the value used to indicate a three-byte length value */ +#define ACPI_PKG_LEN_3_BYTES 0x80 + /** * acpigen_get_current() - Get the current ACPI code output pointer * @@ -65,4 +68,42 @@ void acpigen_emit_stream(struct acpi_ctx *ctx, const char *data, int size); */ void acpigen_emit_string(struct acpi_ctx *ctx, const char *str); +/** + * acpigen_write_len_f() - Write a 'forward' length placeholder + * + * This adds space for a length value in the ACPI stream and pushes the current + * position (before the length) on the stack. After calling this you can write + * some data and then call acpigen_pop_len() to update the length value. + * + * Usage: + * + * acpigen_write_len_f() ------\ + * acpigen_write...() | + * acpigen_write...() | + * acpigen_write_len_f() --\ | + * acpigen_write...() | | + * acpigen_write...() | | + * acpigen_pop_len() ------/ | + * acpigen_write...() | + * acpigen_pop_len() ----------/ + * + * See ACPI 6.3 section 20.2.4 Package Length Encoding + * + * This implementation always uses a 3-byte packet length for simplicity. It + * could be adjusted to support other lengths. + * + * @ctx: ACPI context pointer + */ +void acpigen_write_len_f(struct acpi_ctx *ctx); + +/** + * acpigen_pop_len() - Update the previously stacked length placeholder + * + * Call this after the data for the block has been written. It updates the + * top length value in the stack and pops it off. + * + * @ctx: ACPI context pointer + */ +void acpigen_pop_len(struct acpi_ctx *ctx); + #endif diff --git a/include/dm/acpi.h b/include/dm/acpi.h index 696b1a96a09..dfda88e4931 100644 --- a/include/dm/acpi.h +++ b/include/dm/acpi.h @@ -16,12 +16,15 @@ #define ACPI_OPS_PTR(_ptr) #endif -/* Length of an ACPI name string, excluding nul terminator */ +/* Length of an ACPI name string, excluding null terminator */ #define ACPI_NAME_LEN 4 /* Length of an ACPI name string including nul terminator */ #define ACPI_NAME_MAX (ACPI_NAME_LEN + 1) +/* Number of nested objects supported */ +#define ACPIGEN_LENSTACK_SIZE 10 + #if !defined(__ACPI__) /** @@ -35,6 +38,8 @@ * adding a new table. The RSDP holds pointers to the RSDT and XSDT. * @rsdt: Pointer to the Root System Description Table * @xsdt: Pointer to the Extended System Description Table + * @len_stack: Stack of 'length' words to fix up later + * @ltop: Points to current top of stack (0 = empty) */ struct acpi_ctx { void *base; @@ -42,6 +47,8 @@ struct acpi_ctx { struct acpi_rsdp *rsdp; struct acpi_rsdt *rsdt; struct acpi_xsdt *xsdt; + char *len_stack[ACPIGEN_LENSTACK_SIZE]; + int ltop; }; /** -- cgit v1.3.1