gpio.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 (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 <stdlib.h>
#include <errno.h>
#include <ipxe/gpio.h>

/** @file
 *
 * General purpose I/O
 *
 */

/** List of GPIO controllers */
static LIST_HEAD ( all_gpios );

/**
 * Allocate GPIO controller
 *
 * @v count             Number of GPIO pins
 * @v priv_len          Size of driver-private data
 * @ret gpios           GPIO controller, or NULL
 */
struct gpios * alloc_gpios ( unsigned int count, size_t priv_len ) {
        struct gpios *gpios;
        struct gpio *gpio;
        size_t len;
        unsigned int i;

        /* Allocate and initialise structure */
        len = ( sizeof ( *gpios ) + ( count * sizeof ( *gpio ) ) + priv_len );
        gpios = zalloc ( len );
        if ( ! gpios )
                return NULL;
        gpios->count = count;
        gpios->gpio = ( ( ( void * ) gpios ) + sizeof ( *gpios ) );
        gpios->priv = ( ( ( void * ) gpios ) + sizeof ( *gpios ) +
                        ( count * sizeof ( *gpio ) ) );

        /* Initialise GPIO pins */
        for ( i = 0 ; i < count ; i++ ) {
                gpio = &gpios->gpio[i];
                gpio->gpios = gpios;
                gpio->index = i;
        }

        return gpios;
}

/**
 * Register GPIO controller
 *
 * @v gpios             GPIO controller
 * @ret rc              Return status code
 */
int gpios_register ( struct gpios *gpios ) {

        /* Add to list of GPIO controllers */
        gpios_get ( gpios );
        list_add_tail ( &gpios->list, &all_gpios );
        DBGC ( gpios, "GPIO %s registered with %d GPIOs\n",
               gpios->dev->name, gpios->count );

        return 0;
}

/**
 * Unregister GPIO controller
 *
 * @v gpios             GPIO controller
 */
void gpios_unregister ( struct gpios *gpios ) {

        /* Remove from list of GPIO controllers */
        DBGC ( gpios, "GPIO %s unregistered\n", gpios->dev->name );
        list_del ( &gpios->list );
        gpios_put ( gpios );
}

/**
 * Find GPIO controller
 *
 * @v bus_type          Bus type
 * @v location          Bus location
 * @ret gpios           GPIO controller, or NULL
 */
struct gpios * gpios_find ( unsigned int bus_type, unsigned int location ) {
        struct gpios *gpios;

        /* Scan through list of registered GPIO controllers */
        list_for_each_entry ( gpios, &all_gpios, list ) {
                if ( ( gpios->dev->desc.bus_type == bus_type ) &&
                     ( gpios->dev->desc.location == location ) )
                        return gpios;
        }

        return NULL;
}

/**
 * Get null GPIO input value
 *
 * @v gpios             GPIO controller
 * @v gpio              GPIO pin
 * @ret active          Pin is in the active state
 */
static int null_gpio_in ( struct gpios *gpios __unused,
                          struct gpio *gpio __unused ) {
        return 0;
}

/**
 * Set null GPIO output value
 *
 * @v gpios             GPIO controller
 * @v gpio              GPIO pin
 * @v active            Set pin to active state
 */
static void null_gpio_out ( struct gpios *gpios __unused,
                            struct gpio *gpio __unused, int active __unused ) {
        /* Nothing to do */
}

/**
 * Configure null GPIO pin
 *
 * @v gpios             GPIO controller
 * @v gpio              GPIO pin
 * @v config            Configuration
 * @ret rc              Return status code
 */
static int null_gpio_config ( struct gpios *gpios __unused,
                              struct gpio *gpio __unused,
                              unsigned int config __unused ) {
        return -ENODEV;
}

/** Null GPIO operations */
struct gpio_operations null_gpio_operations = {
        .in = null_gpio_in,
        .out = null_gpio_out,
        .config = null_gpio_config,
};