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    Subject[PATCH 18/19] mfd-core: add platform_device sharing support for mfd

    This adds functions to enable platform_device sharing for mfd clients.

    Each platform driver (mfd client) that wants to share an mfd_cell's
    platform_device uses the mfd_shared_platform_driver_{un,}register()
    functions instead of platform_driver_{un,}register(). Along with
    registering the platform driver, these also register a new platform
    device with the same characteristics as the original, but a different
    name. Given an mfd_cell with the name "foo", the first call to
    mfd_shared_platform_driver_register will register a platform device
    named "foo0", as well as an associated platform_driver named "foo0".
    The second call would register a platform device and driver with the
    name "foo1", and so on.

    This deals with platform handling only; mfd driver-specific details,
    hardware handling, refcounting, etc are all dealt with separately.

    Signed-off-by: Andres Salomon <dilinger@queued.net>
    ---
    drivers/mfd/mfd-core.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/mfd/core.h | 9 ++++
    2 files changed, 124 insertions(+), 0 deletions(-)

    diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
    index 90e9483..a27a377 100644
    --- a/drivers/mfd/mfd-core.c
    +++ b/drivers/mfd/mfd-core.c
    @@ -172,5 +172,120 @@ void mfd_remove_devices(struct device *parent)
    }
    EXPORT_SYMBOL(mfd_remove_devices);

    +/*
    + * Find the first available platform_driver name, appending decimals
    + * after the name. That is, given the string "foo", check whether
    + * "foo0", "foo1", "foo2", etc are in use. Once a name is found
    + * that isn't in use, fill in *newname with it.
    + *
    + * If this returns non-zero, *newname must be kfree()d.
    + */
    +static int get_unique_driver_name(const char *oldname, char **newname)
    +{
    + struct device_driver *drv;
    + char *endp;
    + size_t len;
    + int i;
    +
    + /* allocate memory for new name; includes space for extra 2 digits */
    + len = strlen(oldname);
    + *newname = kmalloc(len + 3, GFP_KERNEL);
    + if (!*newname)
    + return -ENOMEM;
    + endp = strcpy(*newname, oldname) + len;
    + BUG_ON(*endp != '\0');
    +
    + /* search for the first driver name available */
    + for (i = 0; i < 99; i++) {
    + sprintf(endp, "%d", i);
    + drv = driver_find(*newname, &platform_bus_type);
    + if (!drv)
    + break;
    + put_driver(drv);
    + }
    +
    + if (i > 99) {
    + /* we have too many subdevices registered? allow up to 99. */
    + kfree(*newname);
    + return -ENODEV;
    + }
    +
    + return 0;
    +}
    +
    +static int add_shared_platform_device(const char *cell, const char *name)
    +{
    + struct mfd_cell cell_entry;
    + struct device *dev;
    + struct platform_device *pdev;
    + int err;
    +
    + /* check if we've already registered a device (don't fail if we have) */
    + if (bus_find_device_by_name(&platform_bus_type, NULL, name))
    + return 0;
    +
    + /* fetch the parent cell's device (should already be registered!) */
    + dev = bus_find_device_by_name(&platform_bus_type, NULL, cell);
    + if (!dev) {
    + printk(KERN_ERR "failed to find device for cell %s\n", cell);
    + return -ENODEV;
    + }
    + pdev = to_platform_device(dev);
    + memcpy(&cell_entry, mfd_get_cell(pdev), sizeof(cell_entry));
    +
    + WARN_ON(!cell_entry.enable);
    +
    +printk(KERN_WARNING "found cell %s, registering platform device %s\n", cell_entry.name, name);
    + cell_entry.name = name;
    + err = mfd_add_device(pdev->dev.parent, -1, &cell_entry, NULL, 0);
    + if (err)
    + dev_err(dev, "MFD add devices failed: %d\n", err);
    + return err;
    +}
    +
    +int mfd_shared_platform_driver_register(struct platform_driver *drv,
    + const char *cellname)
    +{
    + char *unique = NULL;
    + int err;
    +
    + err = get_unique_driver_name(cellname, &unique);
    + if (err)
    + return err;
    +printk(KERN_WARNING "registering platform device %s\n", unique);
    +
    + err = add_shared_platform_device(cellname, unique);
    + if (err)
    + printk(KERN_ERR "failed to add platform device %s\n", unique);
    +
    +printk(KERN_WARNING "registering platform driver %s\n", unique);
    +
    + drv->driver.name = unique;
    + err = platform_driver_register(drv);
    + if (err)
    + kfree(unique);
    +/* TODO: if cs5535-mfd is already loaded, need to create devices as well */
    +
    + return err;
    +}
    +EXPORT_SYMBOL(mfd_shared_platform_driver_register);
    +
    +void mfd_shared_platform_driver_unregister(struct platform_driver *drv)
    +{
    + struct device *dev;
    +
    +printk(KERN_WARNING "unregistering platform device %s\n", drv->driver.name);
    + dev = bus_find_device_by_name(&platform_bus_type, NULL,
    + drv->driver.name);
    + if (dev)
    + platform_device_unregister(to_platform_device(dev));
    +
    +printk(KERN_WARNING "unregistering platform driver %s\n", drv->driver.name);
    + platform_driver_unregister(drv);
    + kfree(drv->driver.name);
    + drv->driver.name = NULL;
    +}
    +EXPORT_SYMBOL(mfd_shared_platform_driver_unregister);
    +
    MODULE_LICENSE("GPL");
    MODULE_AUTHOR("Ian Molton, Dmitry Baryshkov");
    diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
    index d13b992..ee1dd83 100644
    --- a/include/linux/mfd/core.h
    +++ b/include/linux/mfd/core.h
    @@ -78,4 +78,13 @@ extern int mfd_add_devices(struct device *parent, int id,

    extern void mfd_remove_devices(struct device *parent);

    +/*
    + * For MFD drivers with clients sharing access to resources, these create
    + * multiple platform devices per cell. Contention handling must still be
    + * handled via drivers (ie, with enable/disable hooks).
    + */
    +extern int mfd_shared_platform_driver_register(struct platform_driver *drv,
    + const char *cellname);
    +extern void mfd_shared_platform_driver_unregister(struct platform_driver *drv);
    +
    #endif
    --
    1.7.2.3


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