Antwort: [PATCH v2 13/35] acpigen: Support writing a length
Wolfgang Wallner
wolfgang.wallner at br-automation.com
Tue May 19 15:14:35 CEST 2020
Hi Simon,
-----"Simon Glass" <sjg at chromium.org> schrieb: -----
> Betreff: [PATCH v2 13/35] 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 <sjg at chromium.org>
> ---
>
> Changes in v2: None
> Changes in v1: None
>
> include/acpi/acpigen.h | 3 ++
> include/dm/acpi.h | 7 +++++
> lib/acpi/acpigen.c | 33 ++++++++++++++++++++++
> test/dm/acpigen.c | 64 ++++++++++++++++++++++++++++++++++++++++--
> 4 files changed, 105 insertions(+), 2 deletions(-)
>
> diff --git a/include/acpi/acpigen.h b/include/acpi/acpigen.h
> index 7365cce738..31366f5e34 100644
> --- a/include/acpi/acpigen.h
> +++ b/include/acpi/acpigen.h
> @@ -65,4 +65,7 @@ void acpigen_emit_stream(struct acpi_ctx *ctx, const char *data, int size);
> */
> void acpigen_emit_string(struct acpi_ctx *ctx, const char *str);
>
> +void acpigen_write_len_f(struct acpi_ctx *ctx);
> +void acpigen_pop_len(struct acpi_ctx *ctx);
> +
> #endif
> diff --git a/include/dm/acpi.h b/include/dm/acpi.h
> index 7563a4c60a..2bd03eaa0a 100644
> --- a/include/dm/acpi.h
> +++ b/include/dm/acpi.h
> @@ -22,6 +22,9 @@
> /* 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__)
>
> /**
> @@ -34,12 +37,16 @@
> * 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 *current;
> 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 1223f0d1c4..bd1fa24fb6 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>
>
> @@ -37,6 +38,38 @@ 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] = (0x80 | (len & 0xf));
Nit: Without context this code is hard to understand.
I would propose adding a comment pointing to "ACPI 6.3 20.2.4 Package Length
Encoding" and using a define for 0x80 (something like ACPI_PKG_LEN_3_BYTES ...).
> + 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 3d580a23a5..f9c15b7503 100644
> --- a/test/dm/acpigen.c
> +++ b/test/dm/acpigen.c
> @@ -22,7 +22,7 @@
> #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;
>
> @@ -30,7 +30,8 @@ static int alloc_context(struct acpi_ctx **ctxp)
> ctx = malloc(sizeof(*ctx));
> if (!ctx)
> return -ENOMEM;
> - ctx->current = malloc(150);
> + ctx->current = malloc(size);
> + ctx->ltop = 0;
> if (!ctx->current)
> return -ENOMEM;
> *ctxp = ctx;
> @@ -38,6 +39,11 @@ static int alloc_context(struct acpi_ctx **ctxp)
> return 0;
> }
>
> +static int alloc_context(struct acpi_ctx **ctxp)
> +{
> + return alloc_context_size(ctxp, 150);
> +}
> +
> static void free_context(struct acpi_ctx **ctxp)
> {
> free(*ctxp);
> @@ -334,3 +340,57 @@ 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);
> --
> 2.26.2.645.ge9eca65c58-goog
>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner at br-automation.com>
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