usb_settings.c

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/*
 * Copyright (C) 2024 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 (at your option) 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 );

#include <stdio.h>
#include <errno.h>
#include <ipxe/usb.h>
#include <ipxe/settings.h>
#include <ipxe/init.h>

/** @file
 *
 * USB device settings
 *
 */

/** USB device settings scope */
static const struct settings_scope usb_settings_scope;

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

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

/**
 * Fetch value of USB device 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 usb_settings_fetch ( struct settings *settings __unused,
                                struct setting *setting,
                                void *data, size_t len ) {
        uint8_t *dst = data;
        const uint8_t *src;
        const uint8_t *desc;
        struct usb_bus *bus;
        struct usb_device *usb;
        int tag_direction;
        unsigned int tag_busdev;
        unsigned int tag_offset;
        unsigned int tag_len;
        unsigned int index;
        int rc;

        /* Extract parameters from tag */
        tag_direction = ( ( setting->tag & ( 1 << 31 ) ) ? +1 : -1 );
        tag_busdev = ( ( setting->tag >> 16 ) & 0x7fff );
        tag_offset = ( ( setting->tag >> 8 ) & 0xff );
        tag_len = ( ( setting->tag >> 0 ) & 0xff );

        /* Locate USB device */
        bus = find_usb_bus ( USB_BUS ( tag_busdev ) );
        if ( ! bus )
                return -ENODEV;
        usb = find_usb ( bus, USB_DEV ( tag_busdev ) );
        if ( ! usb )
                return -ENODEV;
        desc = ( ( const uint8_t * ) &usb->device );

        /* Following the usage of SMBIOS settings tags, a <length> of
         * zero indicates that the byte at <offset> contains a string
         * index.  An <offset> of zero indicates that the <length>
         * contains a literal string index.
         *
         * Since the byte at offset zero can never contain a string
         * index, and a literal string index can never be zero, the
         * combination of both <length> and <offset> being zero
         * indicates that the entire structure is to be read.
         *
         * By default we reverse the byte direction since USB values
         * are little-endian and iPXE settings are big-endian.  We
         * invert this default when reading the entire structure.
         */
        if ( ( tag_len == 0 ) && ( tag_offset == 0 ) ) {
                tag_len = sizeof ( usb->device );
                tag_direction = -tag_direction;
        } else if ( ( tag_len == 0 ) || ( tag_offset == 0 ) ) {
                index = tag_len;
                if ( ( ! index ) && ( tag_offset < sizeof ( usb->device ) ) )
                        index = desc[tag_offset];
                if ( ( rc = usb_get_string_descriptor ( usb, index, 0, data,
                                                        len ) ) < 0 ) {
                        return rc;
                }
                if ( ! setting->type )
                        setting->type = &setting_type_string;
                return rc;
        }

        /* Limit length */
        if ( tag_offset > sizeof ( usb->device ) ) {
                tag_len = 0;
        } else if ( ( tag_offset + tag_len ) > sizeof ( usb->device ) ) {
                tag_len = ( sizeof ( usb->device ) - tag_offset );
        }

        /* Copy data, reversing endianness if applicable */
        dst = data;
        src = ( desc + tag_offset );
        if ( tag_direction < 0 )
                src += ( tag_len - 1 );
        if ( len > tag_len )
                len = tag_len;
        for ( ; len-- ; src += tag_direction, dst++ )
                *dst = *src;

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

        return tag_len;
}

/** USB device settings operations */
static struct settings_operations usb_settings_operations = {
        .applies = usb_settings_applies,
        .fetch = usb_settings_fetch,
};

/** USB device settings */
static struct settings usb_settings = {
        .refcnt = NULL,
        .siblings = LIST_HEAD_INIT ( usb_settings.siblings ),
        .children = LIST_HEAD_INIT ( usb_settings.children ),
        .op = &usb_settings_operations,
        .default_scope = &usb_settings_scope,
};

/** Initialise USB device settings */
static void usb_settings_init ( void ) {
        int rc;

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

/** USB device settings initialiser */
struct init_fn usb_settings_init_fn __init_fn ( INIT_NORMAL ) = {
        .initialise = usb_settings_init,
};