devtree.c

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/*
 * Copyright (C) 2025 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
 *
 * Devicetree bus
 *
 */
 
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <ipxe/device.h>
#include <ipxe/fdt.h>
#include <ipxe/iomap.h>
#include <ipxe/devtree.h>
 
static struct dt_driver dt_node_driver __dt_driver;
 
/**
 * Map devicetree range
 *
 * @v dt                Devicetree device
 * @v offset            Starting node offset
 * @v index             Region index
 * @v len               Length to map, or 0 to map whole region
 * @ret io_addr         I/O address, or NULL on error
 */
void * dt_ioremap ( struct dt_device *dt, unsigned int offset,
                    unsigned int index, size_t len ) {
        struct fdt_reg_cells regs;
        uint64_t address;
        uint64_t size;
        void *io_addr;
        int rc;
 
        /* Get parent region cell size specification */
        if ( ( rc = fdt_parent_reg_cells ( &sysfdt, offset, &regs ) ) != 0 ) {
                DBGC ( dt, "DT %s could not get region cell sizes: %s\n",
                       dt->name, strerror ( rc ) );
                return NULL;
        }
 
        /* Read address */
        if ( ( rc = fdt_reg_address ( &sysfdt, offset, &regs, index,
                                      &address ) ) != 0 ) {
                DBGC ( dt, "DT %s could not read region %d address: %s\n",
                       dt->name, index, strerror ( rc ) );
                return NULL;
        }
 
        /* Read size (or assume sufficient, if tree specifies no sizes) */
        size = len;
        if ( regs.size_cells &&
             ( ( rc = fdt_reg_size ( &sysfdt, offset, &regs, index,
                                     &size ) ) != 0 ) ) {
                DBGC ( dt, "DT %s could not read region %d size: %s\n",
                       dt->name, index, strerror ( rc ) );
                return NULL;
        }
 
        /* Use region size as length if not specified */
        if ( ! len )
                len = size;
        DBGC ( dt, "DT %s region %d at %#08llx+%#04llx\n",
               dt->name, index, ( ( unsigned long long ) address ),
               ( ( unsigned long long ) size ) );
 
        /* Verify size */
        if ( len > size ) {
                DBGC ( dt, "DT %s region %d is too small (%#llx/%#zx bytes)\n",
                       dt->name, index, ( ( unsigned long long ) size ), len );
                return NULL;
        }
 
        /* Map region */
        io_addr = ioremap ( address, len );
        if ( ! io_addr ) {
                DBGC ( dt, "DT %s could not map region %d\n",
                       dt->name, index );
                return NULL;
        }
 
        return io_addr;
}
 
/**
 * Find devicetree driver
 *
 * @v dt                Devicetree device
 * @v offset            Starting node offset
 * @ret driver          Driver
 */
static struct dt_driver * dt_find_driver ( struct dt_device *dt,
                                           unsigned int offset ) {
        struct dt_driver *driver;
        const char *ids;
        const char *id;
        unsigned int count;
        unsigned int i;
 
        /* Read compatible programming model identifiers */
        ids = fdt_strings ( &sysfdt, offset, "compatible", &count );
 
        /* Look for a compatible driver */
        for ( id = ids ; count-- ; id += ( strlen ( id ) + 1 ) ) {
                DBGC2 ( &sysfdt, "DT %s is compatible with %s\n",
                        dt->name, id );
                for_each_table_entry ( driver, DT_DRIVERS ) {
                        for ( i = 0 ; i < driver->id_count ; i++ ) {
                                if ( strcmp ( id, driver->ids[i] ) == 0 ) {
                                        DBGC ( dt, "DT %s has %s driver %s\n",
                                               dt->name, id, driver->name );
                                        return driver;
                                }
                        }
                }
        }
 
        /* Use generic node driver if no other driver matches */
        return &dt_node_driver;
}
 
/**
 * Probe devicetree device
 *
 * @v dt                Devicetree device
 * @v offset            Starting node offset
 * @ret rc              Return status code
 */
static int dt_probe ( struct dt_device *dt, unsigned int offset ) {
        struct dt_driver *driver;
        int rc;
 
        /* Identify driver */
        driver = dt_find_driver ( dt, offset );
        dt->driver = driver;
        dt->dev.driver_name = driver->name;
 
        /* Probe device */
        if ( ( rc = driver->probe ( dt, offset ) ) != 0 ) {
                if ( driver != &dt_node_driver ) {
                        DBGC ( dt, "DT %s could not probe: %s\n",
                               dt->name, strerror ( rc ) );
                }
                return rc;
        }
 
        return 0;
}
 
/**
 * Remove devicetree device
 *
 * @v dt                Devicetree device
 */
static void dt_remove ( struct dt_device *dt ) {
        struct dt_driver *driver = dt->driver;
 
        /* Remove device */
        driver->remove ( dt );
        if ( driver != &dt_node_driver )
                DBGC ( dt, "DT %s removed\n", dt->name );
}
 
/**
 * Probe devicetree node
 *
 * @v parent            Parent generic device
 * @v offset            Starting node offset
 * @ret rc              Return status code
 */
int dt_probe_node ( struct device *parent, unsigned int offset ) {
        struct fdt_descriptor desc;
        struct dt_device *dt;
        const char *name;
        int rc;
 
        /* Describe token */
        if ( ( rc = fdt_describe ( &sysfdt, offset, &desc ) ) != 0 )
                goto err_describe;
 
        /* Allocate and initialise device */
        dt = zalloc ( sizeof ( *dt ) );
        if ( ! dt ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        name = ( offset ? desc.name : "root node" );
        dt->name = dt->dev.name;
        snprintf ( dt->dev.name, sizeof ( dt->dev.name ), "%s", name );
        dt->dev.desc.bus_type = BUS_TYPE_DT;
        dt->dev.desc.location = fdt_phandle ( &sysfdt, offset );
        dt->dev.parent = parent;
        INIT_LIST_HEAD ( &dt->dev.children );
        list_add_tail ( &dt->dev.siblings, &parent->children );
 
        /* Probe device */
        if ( ( rc = dt_probe ( dt, offset ) ) != 0 )
                goto err_probe;
 
        return 0;
 
        dt_remove ( dt );
 err_probe:
        list_del ( &dt->dev.siblings );
        free ( dt );
 err_alloc:
 err_describe:
        return rc;
}
 
/**
 * Remove devicetree node
 *
 * @v parent            Parent generic device
 */
void dt_remove_node ( struct device *parent ) {
        struct dt_device *dt;
 
        /* Identify most recently added child */
        dt = list_last_entry ( &parent->children, struct dt_device,
                               dev.siblings );
        assert ( dt != NULL );
 
        /* Remove driver */
        dt_remove ( dt );
 
        /* Delete and free device */
        list_del ( &dt->dev.siblings );
        free ( dt );
}
 
/**
 * Probe devicetree children
 *
 * @v parent            Parent device
 * @v offset            Starting node offset
 * @ret rc              Return status code
 */
int dt_probe_children ( struct dt_device *parent, unsigned int offset ) {
        struct fdt_descriptor desc;
        int depth;
        int rc;
 
        /* Probe any immediate child nodes */
        for ( depth = -1 ; ; depth += desc.depth, offset = desc.next ) {
 
                /* Describe token */
                if ( ( rc = fdt_describe ( &sysfdt, offset, &desc ) ) != 0 ) {
                        DBGC ( &sysfdt, "DT %s has malformed node: %s\n",
                               parent->name, strerror ( rc ) );
                        goto err_describe;
                }
 
                /* Terminate when we exit this node */
                if ( ( depth == 0 ) && ( desc.depth < 0 ) )
                        break;
 
                /* Probe child node, if applicable */
                if ( ( depth == 0 ) && desc.name && ( ! desc.data ) ) {
                        DBGC2 ( &sysfdt, "DT %s is child of %s\n",
                                desc.name, parent->name );
                        dt_probe_node ( &parent->dev, desc.offset );
                }
        }
 
        /* Fail if we have no children (so that this device will be freed) */
        if ( list_empty ( &parent->dev.children ) ) {
                rc = -ENODEV;
                goto err_no_children;
        }
 
        return 0;
 
 err_no_children:
 err_describe:
        dt_remove_children ( parent );
        return rc;
}
 
/**
 * Remove devicetree children
 *
 * @v parent            Parent device
 */
void dt_remove_children ( struct dt_device *parent ) {
 
        /* Remove all child nodes */
        while ( ! list_empty ( &parent->dev.children ) )
                dt_remove_node ( &parent->dev );
}
 
/** Generic node driver */
static struct dt_driver dt_node_driver __dt_driver = {
        .name = "node",
        .probe = dt_probe_children,
        .remove = dt_remove_children,
};
 
/**
 * Probe devicetree bus
 *
 * @v rootdev           Devicetree root device
 * @ret rc              Return status code
 */
static int dt_probe_all ( struct root_device *rootdev ) {
 
        /* Probe root node */
        return dt_probe_node ( &rootdev->dev, 0 );
}
 
/**
 * Remove devicetree bus
 *
 * @v rootdev           Devicetree root device
 */
static void dt_remove_all ( struct root_device *rootdev ) {
 
        /* Remove root node */
        dt_remove_node ( &rootdev->dev );
}
 
/** Devicetree bus root device driver */
static struct root_driver dt_root_driver = {
        .probe = dt_probe_all,
        .remove = dt_remove_all,
};
 
/** Devicetree bus root device */
struct root_device dt_root_device __root_device = {
        .dev = { .name = "DT" },
        .driver = &dt_root_driver,
};