acpi_settings.c

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/*
 * Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/**
 * @file
 *
 * ACPI settings
 *
 */

#include <string.h>
#include <errno.h>
#include <ipxe/init.h>
#include <ipxe/settings.h>
#include <ipxe/acpi.h>

/** ACPI settings scope */
static const struct settings_scope acpi_settings_scope;

/**
 * Check applicability of ACPI setting
 *
 * @v settings          Settings block
 * @v setting           Setting
 * @ret applies         Setting applies within this settings block
 */
static int acpi_settings_applies ( struct settings *settings __unused,
                                   const struct setting *setting ) {

        return ( setting->scope == &acpi_settings_scope );
}

/**
 * Fetch value of ACPI setting
 *
 * @v settings          Settings block
 * @v setting           Setting to fetch
 * @v data              Buffer to fill with setting data
 * @v len               Length of buffer
 * @ret len             Length of setting data, or negative error
 */
static int acpi_settings_fetch ( struct settings *settings,
                                 struct setting *setting,
                                 void *data, size_t len ) {
        const struct acpi_header *acpi;
        const uint8_t *src;
        uint8_t *dst;
        uint32_t tag_high;
        uint32_t tag_low;
        uint32_t tag_signature;
        unsigned int tag_index;
        size_t tag_offset;
        size_t tag_len;
        size_t offset;
        size_t max_len;
        int delta;
        unsigned int i;

        /* Parse settings tag */
        tag_high = ( setting->tag >> 32 );
        tag_low = setting->tag;
        tag_signature = bswap_32 ( tag_high );
        tag_index = ( ( tag_low >> 24 ) & 0xff );
        tag_offset = ( ( tag_low >> 8 ) & 0xffff );
        tag_len = ( ( tag_low >> 0 ) & 0xff );
        DBGC ( settings, "ACPI %s.%d offset %#zx length %#zx\n",
               acpi_name ( tag_signature ), tag_index, tag_offset, tag_len );

        /* Locate ACPI table */
        acpi = acpi_table ( tag_signature, tag_index );
        if ( ! acpi )
                return -ENOENT;

        /* Calculate starting offset and maximum available length */
        max_len = le32_to_cpu ( acpi->length );
        if ( tag_offset > max_len )
                return -ENOENT;
        offset = tag_offset;
        max_len -= offset;

        /* Restrict to requested length, if specified */
        if ( tag_len && ( tag_len < max_len ) )
                max_len = tag_len;

        /* Invert endianness for numeric settings */
        if ( setting->type && setting->type->numerate ) {
                offset += ( max_len - 1 );
                delta = -1;
        } else {
                delta = +1;
        }

        /* Read data */
        src = ( ( ( const void * ) acpi ) + offset );
        dst = data;
        for ( i = 0 ; ( ( i < max_len ) && ( i < len ) ) ; i++ ) {
                *(dst++) = *src;
                src += delta;
        }

        /* Set type if not already specified */
        if ( ! setting->type )
                setting->type = &setting_type_hexraw;

        return max_len;
}

/** ACPI settings operations */
static struct settings_operations acpi_settings_operations = {
        .applies = acpi_settings_applies,
        .fetch = acpi_settings_fetch,
};

/** ACPI settings */
static struct settings acpi_settings = {
        .refcnt = NULL,
        .siblings = LIST_HEAD_INIT ( acpi_settings.siblings ),
        .children = LIST_HEAD_INIT ( acpi_settings.children ),
        .op = &acpi_settings_operations,
        .default_scope = &acpi_settings_scope,
};

/** Initialise ACPI settings */
static void acpi_settings_init ( void ) {
        int rc;

        if ( ( rc = register_settings ( &acpi_settings, NULL,
                                        "acpi" ) ) != 0 ) {
                DBG ( "ACPI could not register settings: %s\n",
                      strerror ( rc ) );
                return;
        }
}

/** ACPI settings initialiser */
struct init_fn acpi_settings_init_fn __init_fn ( INIT_NORMAL ) = {
        .name = "acpi",
        .initialise = acpi_settings_init,
};