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 sjg@chromium.org Reviewed-by: Wolfgang Wallner wolfgang.wallner@br-automation.com ---
Changes in v4: - Add a note about the hard-coded 3-byte length used - Fix 'gas' typo - Use 'null' instead of 'nul'
Changes in v3: - Add a reference to the ACPI spec - Add a define for the 0x80 constant - Move the function comments into this patch
include/acpi/acpigen.h | 41 +++++++++++++++++++++++++++ include/dm/acpi.h | 9 +++++- lib/acpi/acpigen.c | 33 ++++++++++++++++++++++ test/dm/acpigen.c | 64 ++++++++++++++++++++++++++++++++++++++++-- 4 files changed, 144 insertions(+), 3 deletions(-)
diff --git a/include/acpi/acpigen.h b/include/acpi/acpigen.h index 9c1faf7bf2..18409b613c 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 696b1a96a0..dfda88e493 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; };
/** diff --git a/lib/acpi/acpigen.c b/lib/acpi/acpigen.c index 671f1d0eea..11fc38419a 100644 --- a/lib/acpi/acpigen.c +++ b/lib/acpi/acpigen.c @@ -10,6 +10,7 @@
#include <common.h> #include <dm.h> +#include <log.h> #include <acpi/acpigen.h> #include <dm/acpi.h>
@@ -38,6 +39,38 @@ void acpigen_emit_dword(struct acpi_ctx *ctx, uint data) acpigen_emit_byte(ctx, (data >> 24) & 0xff); }
+/* + * Maximum length for an ACPI object generated by this code, + * + * If you need to change this, change acpigen_write_len_f(ctx) and + * acpigen_pop_len(ctx) + */ +#define ACPIGEN_MAXLEN 0xfffff + +void acpigen_write_len_f(struct acpi_ctx *ctx) +{ + assert(ctx->ltop < (ACPIGEN_LENSTACK_SIZE - 1)); + ctx->len_stack[ctx->ltop++] = ctx->current; + acpigen_emit_byte(ctx, 0); + acpigen_emit_byte(ctx, 0); + acpigen_emit_byte(ctx, 0); +} + +void acpigen_pop_len(struct acpi_ctx *ctx) +{ + int len; + char *p; + + assert(ctx->ltop > 0); + p = ctx->len_stack[--ctx->ltop]; + len = ctx->current - (void *)p; + assert(len <= ACPIGEN_MAXLEN); + /* generate store length for 0xfffff max */ + p[0] = ACPI_PKG_LEN_3_BYTES | (len & 0xf); + p[1] = len >> 4 & 0xff; + p[2] = len >> 12 & 0xff; +} + void acpigen_emit_stream(struct acpi_ctx *ctx, const char *data, int size) { int i; diff --git a/test/dm/acpigen.c b/test/dm/acpigen.c index f3d9915500..c756847093 100644 --- a/test/dm/acpigen.c +++ b/test/dm/acpigen.c @@ -25,7 +25,7 @@ #define TEST_STRING "frogmore" #define TEST_STREAM2 "\xfa\xde"
-static int alloc_context(struct acpi_ctx **ctxp) +static int alloc_context_size(struct acpi_ctx **ctxp, int size) { struct acpi_ctx *ctx;
@@ -33,17 +33,23 @@ static int alloc_context(struct acpi_ctx **ctxp) ctx = malloc(sizeof(*ctx)); if (!ctx) return -ENOMEM; - ctx->base = malloc(ACPI_CONTEXT_SIZE); + ctx->base = malloc(size); if (!ctx->base) { free(ctx); return -ENOMEM; } + ctx->ltop = 0; ctx->current = ctx->base; *ctxp = ctx;
return 0; }
+static int alloc_context(struct acpi_ctx **ctxp) +{ + return alloc_context_size(ctxp, ACPI_CONTEXT_SIZE); +} + static void free_context(struct acpi_ctx **ctxp) { free((*ctxp)->base); @@ -344,3 +350,57 @@ static int dm_test_acpi_spi(struct unit_test_state *uts) return 0; } DM_TEST(dm_test_acpi_spi, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT); + +/** + * get_length() - decode a three-byte length field + * + * @ptr: Length encoded as per ACPI + * @return decoded length, or -EINVAL on error + */ +static int get_length(u8 *ptr) +{ + if (!(*ptr & 0x80)) + return -EINVAL; + + return (*ptr & 0xf) | ptr[1] << 4 | ptr[2] << 12; +} + +/* Test emitting a length */ +static int dm_test_acpi_len(struct unit_test_state *uts) +{ + const int size = 0xc0000; + struct acpi_ctx *ctx; + u8 *ptr; + int i; + + ut_assertok(alloc_context_size(&ctx, size)); + + ptr = acpigen_get_current(ctx); + + /* Write a byte and a 3-byte length */ + acpigen_write_len_f(ctx); + acpigen_emit_byte(ctx, 0x23); + acpigen_pop_len(ctx); + ut_asserteq(1 + 3, get_length(ptr)); + + /* Write 200 bytes so we need two length bytes */ + ptr = ctx->current; + acpigen_write_len_f(ctx); + for (i = 0; i < 200; i++) + acpigen_emit_byte(ctx, 0x23); + acpigen_pop_len(ctx); + ut_asserteq(200 + 3, get_length(ptr)); + + /* Write 40KB so we need three length bytes */ + ptr = ctx->current; + acpigen_write_len_f(ctx); + for (i = 0; i < 40000; i++) + acpigen_emit_byte(ctx, 0x23); + acpigen_pop_len(ctx); + ut_asserteq(40000 + 3, get_length(ptr)); + + free_context(&ctx); + + return 0; +} +DM_TEST(dm_test_acpi_len, 0);