[PATCH v3] Add GPIO-based MMC/SD driver - Kernel

This is a discussion on [PATCH v3] Add GPIO-based MMC/SD driver - Kernel ; This driver hooks up the mmc_spi and spi_gpio modules so that MMC/SD cards can be used on a GPIO based bus by bitbanging the SPI protocol in software. This driver provides a configfs interface to dynamically create and destroy GPIO-based ...

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Thread: [PATCH v3] Add GPIO-based MMC/SD driver

  1. [PATCH v3] Add GPIO-based MMC/SD driver

    This driver hooks up the mmc_spi and spi_gpio modules so that
    MMC/SD cards can be used on a GPIO based bus by bitbanging
    the SPI protocol in software.

    This driver provides a configfs interface to dynamically create
    and destroy GPIO-based MMC/SD card interfaces. It also provides
    a platform device interface API.
    See Documentation/gpiommc.txt for details.

    Signed-off-by: Michael Buesch

    ---

    This driver is used in OpenWrt since quite some time, so please
    consider for inclusion in mainline.

    Changes since v2: The sysfs interface has been replaced by a configfs interface.
    Although I don't really like the bloat this adds (this is a driver for embedded
    machines), I do like the much cleaner interface and I think it's worth the bloat.

    Index: linux-next/drivers/mmc/host/gpiommc.c
    ================================================== =================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-next/drivers/mmc/host/gpiommc.c 2008-07-20 21:40:47.000000000 +0200
    @@ -0,0 +1,608 @@
    +/*
    + * Driver an MMC/SD card on a bitbanging GPIO SPI bus.
    + * This module hooks up the mmc_spi and spi_gpio modules and also
    + * provides a configfs interface.
    + *
    + * Copyright 2008 Michael Buesch
    + *
    + * Licensed under the GNU/GPL. See COPYING for details.
    + */
    +
    +#include
    +#include
    +#include
    +#include
    +#include
    +#include
    +#include
    +#include
    +
    +
    +#define PFX "gpio-mmc: "
    +
    +
    +struct gpiommc_device {
    + struct platform_device *pdev;
    + struct platform_device *spi_pdev;
    + struct spi_board_info boardinfo;
    +};
    +
    +
    +MODULE_DESCRIPTION("GPIO based MMC driver");
    +MODULE_AUTHOR("Michael Buesch");
    +MODULE_LICENSE("GPL");
    +
    +
    +static int gpiommc_boardinfo_setup(struct spi_board_info *bi,
    + struct spi_master *master,
    + void *data)
    +{
    + struct gpiommc_device *d = data;
    + struct gpiommc_platform_data *pdata = d->pdev->dev.platform_data;
    +
    + /* Bind the SPI master to the MMC-SPI host driver. */
    + strlcpy(bi->modalias, "mmc_spi", sizeof(bi->modalias));
    +
    + bi->max_speed_hz = pdata->max_bus_speed;
    + bi->bus_num = master->bus_num;
    + bi->mode = pdata->mode;
    +
    + return 0;
    +}
    +
    +static int gpiommc_probe(struct platform_device *pdev)
    +{
    + struct gpiommc_platform_data *mmc_pdata = pdev->dev.platform_data;
    + struct spi_gpio_platform_data spi_pdata;
    + struct gpiommc_device *d;
    + int err;
    +
    + err = -ENXIO;
    + if (!mmc_pdata)
    + goto error;
    +
    +#ifdef CONFIG_MMC_SPI_MODULE
    + err = request_module("mmc_spi");
    + if (err) {
    + printk(KERN_WARNING PFX
    + "Failed to request mmc_spi module.\n");
    + }
    +#endif /* CONFIG_MMC_SPI_MODULE */
    +
    + /* Allocate the GPIO-MMC device */
    + err = -ENOMEM;
    + d = kzalloc(sizeof(*d), GFP_KERNEL);
    + if (!d)
    + goto error;
    + d->pdev = pdev;
    +
    + /* Create the SPI-GPIO device */
    + d->spi_pdev = platform_device_alloc(SPI_GPIO_PLATDEV_NAME,
    + spi_gpio_next_id());
    + if (!d->spi_pdev)
    + goto err_free_d;
    +
    + memset(&spi_pdata, 0, sizeof(spi_pdata));
    + spi_pdata.pin_clk = mmc_pdata->pins.gpio_clk;
    + spi_pdata.pin_miso = mmc_pdata->pins.gpio_do;
    + spi_pdata.pin_mosi = mmc_pdata->pins.gpio_di;
    + spi_pdata.pin_cs = mmc_pdata->pins.gpio_cs;
    + spi_pdata.cs_activelow = mmc_pdata->pins.cs_activelow;
    + spi_pdata.no_spi_delay = mmc_pdata->no_spi_delay;
    + spi_pdata.boardinfo_setup = gpiommc_boardinfo_setup;
    + spi_pdata.boardinfo_setup_data = d;
    +
    + err = platform_device_add_data(d->spi_pdev, &spi_pdata,
    + sizeof(spi_pdata));
    + if (err)
    + goto err_free_pdev;
    + err = platform_device_add(d->spi_pdev);
    + if (err)
    + goto err_free_pdata;
    + platform_set_drvdata(pdev, d);
    +
    + printk(KERN_INFO PFX "MMC-Card \"%s\" "
    + "attached to GPIO pins di=%u, do=%u, clk=%u, cs=%u\n",
    + mmc_pdata->name, mmc_pdata->pins.gpio_di,
    + mmc_pdata->pins.gpio_do,
    + mmc_pdata->pins.gpio_clk,
    + mmc_pdata->pins.gpio_cs);
    +
    + return 0;
    +
    +err_free_pdata:
    + kfree(d->spi_pdev->dev.platform_data);
    + d->spi_pdev->dev.platform_data = NULL;
    +err_free_pdev:
    + platform_device_put(d->spi_pdev);
    +err_free_d:
    + kfree(d);
    +error:
    + return err;
    +}
    +
    +static int gpiommc_remove(struct platform_device *pdev)
    +{
    + struct gpiommc_device *d = platform_get_drvdata(pdev);
    + struct gpiommc_platform_data *pdata = d->pdev->dev.platform_data;
    +
    + platform_device_unregister(d->spi_pdev);
    + printk(KERN_INFO PFX "GPIO based MMC-Card \"%s\" removed\n",
    + pdata->name);
    + platform_device_put(d->spi_pdev);
    +
    + return 0;
    +}
    +
    +#ifdef CONFIG_GPIOMMC_CONFIGFS
    +
    +/* A device that was created through configfs */
    +struct gpiommc_configfs_device {
    + struct config_item item;
    + /* The platform device, after registration. */
    + struct platform_device *pdev;
    + /* The configuration */
    + struct gpiommc_platform_data pdata;
    +};
    +
    +#define GPIO_INVALID -1
    +
    +static inline bool gpiommc_is_registered(struct gpiommc_configfs_device *dev)
    +{
    + return (dev->pdev != NULL);
    +}
    +
    +static inline struct gpiommc_configfs_device *ci_to_gpiommc(struct config_item *item)
    +{
    + return item ? container_of(item, struct gpiommc_configfs_device, item) : NULL;
    +}
    +
    +static struct configfs_attribute gpiommc_attr_DI = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "gpio_data_in",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_DO = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "gpio_data_out",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_CLK = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "gpio_clock",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_CS = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "gpio_chipselect",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_CS_activelow = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "gpio_chipselect_activelow",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_spimode = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "spi_mode",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_spidelay = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "spi_delay",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_max_bus_speed = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "max_bus_speed",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute gpiommc_attr_register = {
    + .ca_owner = THIS_MODULE,
    + .ca_name = "register",
    + .ca_mode = S_IRUGO | S_IWUSR,
    +};
    +
    +static struct configfs_attribute *gpiommc_config_attrs[] = {
    + &gpiommc_attr_DI,
    + &gpiommc_attr_DO,
    + &gpiommc_attr_CLK,
    + &gpiommc_attr_CS,
    + &gpiommc_attr_CS_activelow,
    + &gpiommc_attr_spimode,
    + &gpiommc_attr_spidelay,
    + &gpiommc_attr_max_bus_speed,
    + &gpiommc_attr_register,
    + NULL,
    +};
    +
    +static ssize_t gpiommc_config_attr_show(struct config_item *item,
    + struct configfs_attribute *attr,
    + char *page)
    +{
    + struct gpiommc_configfs_device *dev = ci_to_gpiommc(item);
    + ssize_t count = 0;
    + unsigned int gpio;
    + int err = 0;
    +
    + if (attr == &gpiommc_attr_DI) {
    + gpio = dev->pdata.pins.gpio_di;
    + if (gpio == GPIO_INVALID)
    + count = snprintf(page, PAGE_SIZE, "not configured\n");
    + else
    + count = snprintf(page, PAGE_SIZE, "%u\n", gpio);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_DO) {
    + gpio = dev->pdata.pins.gpio_do;
    + if (gpio == GPIO_INVALID)
    + count = snprintf(page, PAGE_SIZE, "not configured\n");
    + else
    + count = snprintf(page, PAGE_SIZE, "%u\n", gpio);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CLK) {
    + gpio = dev->pdata.pins.gpio_clk;
    + if (gpio == GPIO_INVALID)
    + count = snprintf(page, PAGE_SIZE, "not configured\n");
    + else
    + count = snprintf(page, PAGE_SIZE, "%u\n", gpio);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CS) {
    + gpio = dev->pdata.pins.gpio_cs;
    + if (gpio == GPIO_INVALID)
    + count = snprintf(page, PAGE_SIZE, "not configured\n");
    + else
    + count = snprintf(page, PAGE_SIZE, "%u\n", gpio);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CS_activelow) {
    + count = snprintf(page, PAGE_SIZE, "%u\n",
    + dev->pdata.pins.cs_activelow);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_spimode) {
    + count = snprintf(page, PAGE_SIZE, "%u\n",
    + dev->pdata.mode);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_spidelay) {
    + count = snprintf(page, PAGE_SIZE, "%u\n",
    + !dev->pdata.no_spi_delay);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_max_bus_speed) {
    + count = snprintf(page, PAGE_SIZE, "%u\n",
    + dev->pdata.max_bus_speed);
    + goto out;
    + }
    + if (attr == &gpiommc_attr_register) {
    + count = snprintf(page, PAGE_SIZE, "%u\n",
    + gpiommc_is_registered(dev));
    + goto out;
    + }
    + WARN_ON(1);
    + err = -ENOSYS;
    +out:
    + return err ? err : count;
    +}
    +
    +static int gpiommc_do_register(struct gpiommc_configfs_device *dev,
    + const char *name)
    +{
    + int err;
    +
    + if (gpiommc_is_registered(dev))
    + return 0;
    +
    + if (!gpio_is_valid(dev->pdata.pins.gpio_di) ||
    + !gpio_is_valid(dev->pdata.pins.gpio_do) ||
    + !gpio_is_valid(dev->pdata.pins.gpio_clk) ||
    + !gpio_is_valid(dev->pdata.pins.gpio_cs)) {
    + printk(KERN_ERR PFX
    + "configfs: Invalid GPIO pin number(s)\n");
    + return -EINVAL;
    + }
    +
    + strlcpy(dev->pdata.name, name,
    + sizeof(dev->pdata.name));
    +
    + dev->pdev = platform_device_alloc(GPIOMMC_PLATDEV_NAME,
    + gpiommc_next_id());
    + if (!dev->pdev)
    + return -ENOMEM;
    + err = platform_device_add_data(dev->pdev, &dev->pdata,
    + sizeof(dev->pdata));
    + if (err) {
    + platform_device_put(dev->pdev);
    + return err;
    + }
    + err = platform_device_add(dev->pdev);
    + if (err) {
    + platform_device_put(dev->pdev);
    + return err;
    + }
    +
    + return 0;
    +}
    +
    +static void gpiommc_do_unregister(struct gpiommc_configfs_device *dev)
    +{
    + if (!gpiommc_is_registered(dev))
    + return;
    +
    + platform_device_unregister(dev->pdev);
    + dev->pdev = NULL;
    +}
    +
    +static ssize_t gpiommc_config_attr_store(struct config_item *item,
    + struct configfs_attribute *attr,
    + const char *page, size_t count)
    +{
    + struct gpiommc_configfs_device *dev = ci_to_gpiommc(item);
    + int err = -EINVAL;
    + unsigned long data;
    +
    + if (attr == &gpiommc_attr_register) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (data == 1)
    + err = gpiommc_do_register(dev, item->ci_name);
    + if (data == 0) {
    + gpiommc_do_unregister(dev);
    + err = 0;
    + }
    + goto out;
    + }
    +
    + if (gpiommc_is_registered(dev)) {
    + /* The rest of the config parameters can only be set
    + * as long as the device is not registered, yet. */
    + err = -EBUSY;
    + goto out;
    + }
    +
    + if (attr == &gpiommc_attr_DI) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (!gpio_is_valid(data))
    + goto out;
    + dev->pdata.pins.gpio_di = data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_DO) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (!gpio_is_valid(data))
    + goto out;
    + dev->pdata.pins.gpio_do = data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CLK) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (!gpio_is_valid(data))
    + goto out;
    + dev->pdata.pins.gpio_clk = data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CS) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (!gpio_is_valid(data))
    + goto out;
    + dev->pdata.pins.gpio_cs = data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_CS_activelow) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (data != 0 && data != 1)
    + goto out;
    + dev->pdata.pins.cs_activelow = data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_spimode) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + switch (data) {
    + case 0:
    + dev->pdata.mode = SPI_MODE_0;
    + break;
    + case 1:
    + dev->pdata.mode = SPI_MODE_1;
    + break;
    + case 2:
    + dev->pdata.mode = SPI_MODE_2;
    + break;
    + case 3:
    + dev->pdata.mode = SPI_MODE_3;
    + break;
    + default:
    + goto out;
    + }
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_spidelay) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (data != 0 && data != 1)
    + goto out;
    + dev->pdata.no_spi_delay = !data;
    + err = 0;
    + goto out;
    + }
    + if (attr == &gpiommc_attr_max_bus_speed) {
    + err = strict_strtoul(page, 10, &data);
    + if (err)
    + goto out;
    + err = -EINVAL;
    + if (data > UINT_MAX)
    + goto out;
    + dev->pdata.max_bus_speed = data;
    + err = 0;
    + goto out;
    + }
    + WARN_ON(1);
    + err = -ENOSYS;
    +out:
    + return err ? err : count;
    +}
    +
    +static void gpiommc_config_item_release(struct config_item *item)
    +{
    + struct gpiommc_configfs_device *dev = ci_to_gpiommc(item);
    +
    + kfree(dev);
    +}
    +
    +static struct configfs_item_operations gpiommc_config_item_ops = {
    + .release = gpiommc_config_item_release,
    + .show_attribute = gpiommc_config_attr_show,
    + .store_attribute = gpiommc_config_attr_store,
    +};
    +
    +static struct config_item_type gpiommc_dev_ci_type = {
    + .ct_item_ops = &gpiommc_config_item_ops,
    + .ct_attrs = gpiommc_config_attrs,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct config_item *gpiommc_make_item(struct config_group *group,
    + const char *name)
    +{
    + struct gpiommc_configfs_device *dev;
    +
    + if (strlen(name) > GPIOMMC_MAX_NAMELEN) {
    + printk(KERN_ERR PFX "configfs: device name too long\n");
    + return NULL;
    + }
    +
    + dev = kzalloc(sizeof(*dev), GFP_KERNEL);
    + if (!dev)
    + return NULL;
    +
    + config_item_init_type_name(&dev->item, name,
    + &gpiommc_dev_ci_type);
    +
    + /* Assign default configuration */
    + dev->pdata.pins.gpio_di = GPIO_INVALID;
    + dev->pdata.pins.gpio_do = GPIO_INVALID;
    + dev->pdata.pins.gpio_clk = GPIO_INVALID;
    + dev->pdata.pins.gpio_cs = GPIO_INVALID;
    + dev->pdata.pins.cs_activelow = 1;
    + dev->pdata.mode = SPI_MODE_0;
    + dev->pdata.no_spi_delay = 0;
    + dev->pdata.max_bus_speed = 5000000; /* 5 MHz */
    +
    + return &(dev->item);
    +}
    +
    +static void gpiommc_drop_item(struct config_group *group,
    + struct config_item *item)
    +{
    + struct gpiommc_configfs_device *dev = ci_to_gpiommc(item);
    +
    + gpiommc_do_unregister(dev);
    + kfree(dev);
    +}
    +
    +static struct configfs_group_operations gpiommc_ct_group_ops = {
    + .make_item = gpiommc_make_item,
    + .drop_item = gpiommc_drop_item,
    +};
    +
    +static struct config_item_type gpiommc_ci_type = {
    + .ct_group_ops = &gpiommc_ct_group_ops,
    + .ct_owner = THIS_MODULE,
    +};
    +
    +static struct configfs_subsystem gpiommc_subsys = {
    + .su_group = {
    + .cg_item = {
    + .ci_namebuf = GPIOMMC_PLATDEV_NAME,
    + .ci_type = &gpiommc_ci_type,
    + },
    + },
    + .su_mutex = __MUTEX_INITIALIZER(gpiommc_subsys.su_mutex),
    +};
    +
    +#endif /* CONFIG_GPIOMMC_CONFIGFS */
    +
    +static struct platform_driver gpiommc_plat_driver = {
    + .probe = gpiommc_probe,
    + .remove = gpiommc_remove,
    + .driver = {
    + .name = GPIOMMC_PLATDEV_NAME,
    + .owner = THIS_MODULE,
    + },
    +};
    +
    +int gpiommc_next_id(void)
    +{
    + static atomic_t counter = ATOMIC_INIT(-1);
    +
    + return atomic_inc_return(&counter);
    +}
    +EXPORT_SYMBOL(gpiommc_next_id);
    +
    +static int __init gpiommc_modinit(void)
    +{
    + int err;
    +
    + err = platform_driver_register(&gpiommc_plat_driver);
    + if (err)
    + return err;
    +
    +#ifdef CONFIG_GPIOMMC_CONFIGFS
    + config_group_init(&gpiommc_subsys.su_group);
    + err = configfs_register_subsystem(&gpiommc_subsys);
    + if (err) {
    + platform_driver_unregister(&gpiommc_plat_driver);
    + return err;
    + }
    +#endif /* CONFIG_GPIOMMC_CONFIGFS */
    +
    + return 0;
    +}
    +module_init(gpiommc_modinit);
    +
    +static void __exit gpiommc_modexit(void)
    +{
    +#ifdef CONFIG_GPIOMMC_CONFIGFS
    + configfs_unregister_subsystem(&gpiommc_subsys);
    +#endif
    + platform_driver_unregister(&gpiommc_plat_driver);
    +}
    +module_exit(gpiommc_modexit);
    Index: linux-next/drivers/mmc/host/Kconfig
    ================================================== =================
    --- linux-next.orig/drivers/mmc/host/Kconfig 2008-07-20 21:39:09.000000000 +0200
    +++ linux-next/drivers/mmc/host/Kconfig 2008-07-20 21:40:47.000000000 +0200
    @@ -174,3 +174,27 @@ config MMC_SDRICOH_CS
    To compile this driver as a module, choose M here: the
    module will be called sdricoh_cs.

    +config GPIOMMC
    + tristate "MMC/SD over GPIO-based SPI"
    + depends on MMC && MMC_SPI && SPI_GPIO
    + help
    + This driver hooks up the mmc_spi and spi_gpio modules so that
    + MMC/SD cards can be used on a GPIO based bus by bitbanging
    + the SPI protocol in software.
    +
    + This driver provides a configfs interface to dynamically create
    + and destroy GPIO-based MMC/SD card devices. It also provides
    + a platform device interface API.
    + See Documentation/gpiommc.txt for details.
    +
    + The module will be called gpiommc.
    +
    + If unsure, say N.
    +
    +config GPIOMMC_CONFIGFS
    + bool
    + depends on GPIOMMC && CONFIGFS_FS
    + default y
    + help
    + This option automatically enables configfs support for gpiommc
    + if configfs is available.
    Index: linux-next/drivers/mmc/host/Makefile
    ================================================== =================
    --- linux-next.orig/drivers/mmc/host/Makefile 2008-07-20 21:39:09.000000000 +0200
    +++ linux-next/drivers/mmc/host/Makefile 2008-07-20 21:41:26.000000000 +0200
    @@ -21,4 +21,4 @@ obj-$(CONFIG_MMC_TIFM_SD) += tifm_sd.o
    obj-$(CONFIG_MMC_SPI) += mmc_spi.o
    obj-$(CONFIG_MMC_S3C) += s3cmci.o
    obj-$(CONFIG_MMC_SDRICOH_CS) += sdricoh_cs.o
    -
    +obj-$(CONFIG_GPIOMMC) += gpiommc.o
    Index: linux-next/include/linux/mmc/gpiommc.h
    ================================================== =================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-next/include/linux/mmc/gpiommc.h 2008-07-20 21:40:47.000000000 +0200
    @@ -0,0 +1,71 @@
    +/*
    + * Device driver for MMC/SD cards driven over a GPIO bus.
    + *
    + * Copyright (c) 2008 Michael Buesch
    + *
    + * Licensed under the GNU/GPL version 2.
    + */
    +#ifndef LINUX_GPIOMMC_H_
    +#define LINUX_GPIOMMC_H_
    +
    +#include
    +
    +
    +#define GPIOMMC_MAX_NAMELEN 15
    +#define GPIOMMC_MAX_NAMELEN_STR __stringify(GPIOMMC_MAX_NAMELEN)
    +
    +/**
    + * struct gpiommc_pins - Hardware pin assignments
    + *
    + * @gpio_di: The GPIO number of the DATA IN pin
    + * @gpio_do: The GPIO number of the DATA OUT pin
    + * @gpio_clk: The GPIO number of the CLOCK pin
    + * @gpio_cs: The GPIO number of the CHIPSELECT pin
    + * @cs_activelow: If true, the chip is considered selected if @gpio_cs is low.
    + */
    +struct gpiommc_pins {
    + unsigned int gpio_di;
    + unsigned int gpio_do;
    + unsigned int gpio_clk;
    + unsigned int gpio_cs;
    + bool cs_activelow;
    +};
    +
    +/**
    + * struct gpiommc_platform_data - Platform data for a MMC-over-SPI-GPIO device.
    + *
    + * @name: The unique name string of the device.
    + * @pins: The hardware pin assignments.
    + * @mode: The hardware mode. This is either SPI_MODE_0,
    + * SPI_MODE_1, SPI_MODE_2 or SPI_MODE_3. See the SPI documentation.
    + * @no_spi_delay: Do not use delays in the lowlevel SPI bitbanging code.
    + * This is not standards compliant, but may be required for some
    + * embedded machines to gain reasonable speed.
    + * @max_bus_speed: The maximum speed of the SPI bus, in Hertz.
    + */
    +struct gpiommc_platform_data {
    + char name[GPIOMMC_MAX_NAMELEN + 1];
    + struct gpiommc_pins pins;
    + u8 mode;
    + bool no_spi_delay;
    + unsigned int max_bus_speed;
    +};
    +
    +/**
    + * GPIOMMC_PLATDEV_NAME - The platform device name string.
    + *
    + * The name string that has to be used for platform_device_alloc
    + * when allocating a gpiommc device.
    + */
    +#define GPIOMMC_PLATDEV_NAME "gpiommc"
    +
    +/**
    + * gpiommc_next_id - Get another platform device ID number.
    + *
    + * This returns the next platform device ID number that has to be used
    + * for platform_device_alloc. The ID is opaque and should not be used for
    + * anything else.
    + */
    +int gpiommc_next_id(void);
    +
    +#endif /* LINUX_GPIOMMC_H_ */
    Index: linux-next/Documentation/gpiommc.txt
    ================================================== =================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-next/Documentation/gpiommc.txt 2008-07-20 21:40:47.000000000 +0200
    @@ -0,0 +1,97 @@
    +GPIOMMC - Driver for an MMC/SD card on a bitbanging GPIO SPI bus
    +================================================= ===============
    +
    +The gpiommc module hooks up the mmc_spi and spi_gpio modules for running an
    +MMC or SD card on GPIO pins.
    +
    +Two interfaces for registering a new MMC/SD card device are provided:
    +A static platform-device based mechanism and a dynamic configfs based interface.
    +
    +
    +Registering devices via platform-device
    +=======================================
    +
    +The platform-device interface is used for registering MMC/SD devices that are
    +part of the hardware platform. This is most useful only for embedded machines
    +with MMC/SD devices statically connected to the platform GPIO bus.
    +
    +The data structures are declared in .
    +
    +To register a new device, define an instance of struct gpiommc_platform_data.
    +This structure holds any information about how the device is hooked up to the
    +GPIO pins and what hardware modes the device supports. See the docbook-style
    +documentation in the header file for more information on the struct fields.
    +
    +Then allocate a new instance of a platform device by doing:
    +
    + pdev = platform_device_alloc(GPIOMMC_PLATDEV_NAME, gpiommc_next_id());
    +
    +This will allocate the platform device data structures and hook it up to the
    +gpiommc driver.
    +Then add the gpiommc_platform_data to the platform device.
    +
    + err = platform_device_add_data(pdev, pdata, sizeof(struct gpiommc_platform_data));
    +
    +You may free the local instance of struct gpiommc_platform_data now. (So the
    +struct may be allocated on the stack, too).
    +Now simply register the platform device.
    +
    + err = platform_device_add(pdev);
    +
    +Done. The gpiommc probe routine will be invoked now and you should see a kernel
    +log message for the added device.
    +
    +
    +Registering devices via configfs
    +================================
    +
    +MMC/SD cards connected via GPIO often are a pretty dynamic thing, as for example
    +selfmade hacks for soldering an MMC/SD card to standard GPIO pins on embedded
    +hardware are a common situation.
    +So we provide a dynamic interface to conveniently handle adding and removing
    +devices from userspace, without the need to recompile the kernel.
    +
    +The "gpiommc" subdirectory at the configfs mountpoint is used for handling
    +the dynamic configuration.
    +
    +To create a new device, it must first be allocated with mkdir.
    +The following command will allocate a device named "my_mmc":
    + mkdir /config/gpiommc/my_mmc
    +
    +There are several configuration files available in the new
    +/config/gpiommc/my_mmc/ directory:
    +
    +gpio_data_in = The SPI data-IN GPIO pin number.
    +gpio_data_out = The SPI data-OUT GPIO pin number.
    +gpio_clock = The SPI Clock GPIO pin number.
    +gpio_chipselect = The SPI Chipselect GPIO pin number.
    +gpio_chipselect_activelow = Boolean. If 0, Chipselect is active-HIGH.
    + If 1, Chipselect is active-LOW.
    +spi_mode = The SPI data mode. Can be 0-3.
    +spi_delay = Enable all delays in the lowlevel bitbanging.
    +max_bus_speed = The maximum SPI bus speed. In Hertz.
    +
    +register = Not a configuration parameter.
    + Used to register the configured card
    + with the kernel.
    +
    +The device must first get configured and then registered by writing "1" to
    +the "register" file.
    +The configuration parameters "gpio_data_in", "gpio_data_out", "gpio_clock"
    +and "gpio_chipselect" are essential and _must_ be configured before writing
    +"1" to the "register" file. The registration will fail, otherwise.
    +
    +The default values for the other parameters are:
    +gpio_chipselect_activelow = 1 (CS active-LOW)
    +spi_mode = 0 (SPI_MODE_0)
    +spi_delay = 1 (enabled)
    +max_bus_speed = 5000000 (5 Mhz)
    +
    +Configuration values can not be changed after registration. To unregister
    +the device, write a "0" to the "register" file. The configuration can be
    +changed again after unregistering.
    +
    +To completely remove the device, simply rmdir the directory
    +(/config/gpiommc/my_mmc in this example).
    +There's no need to first unregister the device before removing it. That will
    +be done automatically.
    Index: linux-next/MAINTAINERS
    ================================================== =================
    --- linux-next.orig/MAINTAINERS 2008-07-20 21:40:38.000000000 +0200
    +++ linux-next/MAINTAINERS 2008-07-20 21:40:47.000000000 +0200
    @@ -1880,6 +1880,11 @@ L: gigaset307x-common@lists.sourceforge.
    W: http://gigaset307x.sourceforge.net/
    S: Maintained

    +GPIOMMC DRIVER
    +P: Michael Buesch
    +M: mb@bu3sch.de
    +S: Maintained
    +
    HARDWARE MONITORING
    P: Mark M. Hoffman
    M: mhoffman@lightlink.com

    --
    Greetings Michael.
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  2. Re: [PATCH v3] Add GPIO-based MMC/SD driver

    On Sun, 20 Jul 2008 21:48:58 +0200 Michael Buesch wrote:

    > This driver hooks up the mmc_spi and spi_gpio modules so that
    > MMC/SD cards can be used on a GPIO based bus by bitbanging
    > the SPI protocol in software.
    >
    > This driver provides a configfs interface to dynamically create
    > and destroy GPIO-based MMC/SD card interfaces. It also provides
    > a platform device interface API.
    > See Documentation/gpiommc.txt for details.
    >
    > Signed-off-by: Michael Buesch
    >
    > ---
    >
    > This driver is used in OpenWrt since quite some time, so please
    > consider for inclusion in mainline.
    >
    > Changes since v2: The sysfs interface has been replaced by a configfs interface.
    > Although I don't really like the bloat this adds (this is a driver for embedded
    > machines), I do like the much cleaner interface and I think it's worth the bloat.


    > Index: linux-next/Documentation/gpiommc.txt
    > ================================================== =================
    > --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    > +++ linux-next/Documentation/gpiommc.txt 2008-07-20 21:40:47.000000000 +0200
    > @@ -0,0 +1,97 @@


    ....

    One minor nit below, otherwise looks good to me.
    Thanks.


    > +Registering devices via configfs
    > +================================
    > +
    > +MMC/SD cards connected via GPIO often are a pretty dynamic thing, as for example
    > +selfmade hacks for soldering an MMC/SD card to standard GPIO pins on embedded
    > +hardware are a common situation.
    > +So we provide a dynamic interface to conveniently handle adding and removing
    > +devices from userspace, without the need to recompile the kernel.
    > +
    > +The "gpiommc" subdirectory at the configfs mountpoint is used for handling
    > +the dynamic configuration.
    > +
    > +To create a new device, it must first be allocated with mkdir.
    > +The following command will allocate a device named "my_mmc":
    > + mkdir /config/gpiommc/my_mmc
    > +
    > +There are several configuration files available in the new
    > +/config/gpiommc/my_mmc/ directory:
    > +
    > +gpio_data_in = The SPI data-IN GPIO pin number.
    > +gpio_data_out = The SPI data-OUT GPIO pin number.
    > +gpio_clock = The SPI Clock GPIO pin number.
    > +gpio_chipselect = The SPI Chipselect GPIO pin number.
    > +gpio_chipselect_activelow = Boolean. If 0, Chipselect is active-HIGH.
    > + If 1, Chipselect is active-LOW.
    > +spi_mode = The SPI data mode. Can be 0-3.



    > +spi_delay = Enable all delays in the lowlevel bitbanging.
    > +max_bus_speed = The maximum SPI bus speed. In Hertz.
    > +
    > +register = Not a configuration parameter.
    > + Used to register the configured card
    > + with the kernel.
    > +
    > +The device must first get configured and then registered by writing "1" to
    > +the "register" file.
    > +The configuration parameters "gpio_data_in", "gpio_data_out", "gpio_clock"
    > +and "gpio_chipselect" are essential and _must_ be configured before writing
    > +"1" to the "register" file. The registration will fail, otherwise.
    > +
    > +The default values for the other parameters are:
    > +gpio_chipselect_activelow = 1 (CS active-LOW)
    > +spi_mode = 0 (SPI_MODE_0)
    > +spi_delay = 1 (enabled)
    > +max_bus_speed = 5000000 (5 Mhz)
    > +
    > +Configuration values can not be changed after registration. To unregister


    cannot

    > +the device, write a "0" to the "register" file. The configuration can be
    > +changed again after unregistering.



    ---
    ~Randy
    Linux Plumbers Conference, 17-19 September 2008, Portland, Oregon USA
    http://linuxplumbersconf.org/
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  3. Re: [PATCH v3] Add GPIO-based MMC/SD driver

    On Sun, Jul 20, 2008 at 09:48:58PM +0200, Michael Buesch wrote:
    > This driver hooks up the mmc_spi and spi_gpio modules so that
    > MMC/SD cards can be used on a GPIO based bus by bitbanging
    > the SPI protocol in software.
    >
    > This driver provides a configfs interface to dynamically create
    > and destroy GPIO-based MMC/SD card interfaces. It also provides
    > a platform device interface API.
    > See Documentation/gpiommc.txt for details.


    configfs stuff should still go in Documentation/ABI as it is a
    userspace/kernelspace interface.

    thanks,

    greg k-h
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