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Date: Tue, 03 Aug 2010 16:36:48 -0700
From: Patrick Pannuto <ppannuto@...eaurora.org>
To: linux-kernel@...r.kernel.org
CC: linux-arm-msm@...r.kernel.org, linux-omap@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...e.de>, damm@...nsource.se,
lethal@...ux-sh.org, rjw@...k.pl, dtor@...l.ru,
eric.y.miao@...il.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] platform: Faciliatate the creation of pseduo-platform
busses
Mis-typed omap's list; sorry for the resend
On 08/03/2010 04:35 PM, Patrick Pannuto wrote:
> Inspiration for this comes from:
> http://www.mail-archive.com/linux-omap@vger.kernel.org/msg31161.html
>
> INTRO
>
> As SOCs become more popular, the desire to quickly define a simple,
> but functional, bus type with only a few unique properties becomes
> desirable. As they become more complicated, the ability to nest these
> simple busses and otherwise orchestrate them to match the actual
> topology also becomes desirable.
>
> EXAMPLE USAGE
>
> /arch/ARCH/MY_ARCH/my_bus.c:
>
> #include <linux/device.h>
> #include <linux/platform_device.h>
>
> struct bus_type my_bus_type = {
> .name = "mybus",
> };
> EXPORT_SYMBOL_GPL(my_bus_type);
>
> struct platform_device sub_bus1 = {
> .name = "sub_bus1",
> .id = -1,
> .dev.bus = &my_bus_type,
> }
> EXPORT_SYMBOL_GPL(sub_bus1);
>
> struct platform_device sub_bus2 = {
> .name = "sub_bus2",
> .id = -1,
> .dev.bus = &my_bus_type,
> }
> EXPORT_SYMBOL_GPL(sub_bus2);
>
> static int __init my_bus_init(void)
> {
> int error;
> platform_bus_type_init(&my_bus_type);
>
> error = bus_register(&my_bus_type);
> if (error)
> return error;
>
> error = platform_device_register(&sub_bus1);
> if (error)
> goto fail_sub_bus1;
>
> error = platform_device_register(&sub_bus2);
> if (error)
> goto fail_sub_bus2;
>
> return error;
>
> fail_sub_bus2:
> platform_device_unregister(&sub_bus1);
> fail_sub_bus2:
> bus_unregister(&my_bus_type);
>
> return error;
> }
> postcore_initcall(my_bus_init);
> EXPORT_SYMBOL_CPY(my_bus_init);
>
> /drivers/my_driver.c
> static struct platform_driver my_driver = {
> .driver = {
> .name = "my-driver",
> .owner = THIS_MODULE,
> .bus = &my_bus_type,
> },
> };
>
> /somewhere/my_device.c
> static struct platform_device my_device = {
> .name = "my-device",
> .id = -1,
> .dev.bus = &my_bus_type,
> .dev.parent = &sub_bus_1.dev,
> };
>
> Notice that for a device / driver, only 3 lines were added to
> switch from the platform bus to the new my_bus. This is
> especially valuable if we consider supporting a legacy SOCs
> and new SOCs where the same driver is used, but may need to
> be on either the platform bus or the new my_bus. The above
> code then becomes:
>
> (possibly in a header)
> #ifdef CONFIG_MY_BUS
> #define MY_BUS_TYPE &my_bus_type
> #else
> #define MY_BUS_TYPE NULL
> #endif
>
> /drivers/my_driver.c
> static struct platform_driver my_driver = {
> .driver = {
> .name = "my-driver",
> .owner = THIS_MODULE,
> .bus = MY_BUS_TYPE,
> },
> };
>
> Which will allow the same driver to easily to used on either
> the platform bus or the newly defined bus type.
>
> This will build a device tree that mirrors the actual configuration:
> /sys/bus
> |-- my_bus
> | |-- devices
> | | |-- sub_bus1 -> ../../../devices/platform/sub_bus1
> | | |-- sub_bus2 -> ../../../devices/platform/sub_bus2
> | | |-- my-device -> ../../../devices/platform/sub_bus1/my-device
> | |-- drivers
> | | |-- my-driver
>
> I believe this to be a fairly elegant and simple solution to the
> problem, but humbly RFC
>
> -Pat
>
> Signed-off-by: Patrick Pannuto <ppannuto@...eaurora.org>
> ---
> drivers/base/platform.c | 30 ++++++++++++++++++++++++++----
> include/linux/platform_device.h | 2 ++
> 2 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 4d99c8b..c86be03 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -241,7 +241,8 @@ int platform_device_add(struct platform_device *pdev)
> if (!pdev->dev.parent)
> pdev->dev.parent = &platform_bus;
>
> - pdev->dev.bus = &platform_bus_type;
> + if (!pdev->dev.bus)
> + pdev->dev.bus = &platform_bus_type;
>
> if (pdev->id != -1)
> dev_set_name(&pdev->dev, "%s.%d", pdev->name, pdev->id);
> @@ -482,7 +483,8 @@ static void platform_drv_shutdown(struct device *_dev)
> */
> int platform_driver_register(struct platform_driver *drv)
> {
> - drv->driver.bus = &platform_bus_type;
> + if (!drv->driver.bus)
> + drv->driver.bus = &platform_bus_type;
> if (drv->probe)
> drv->driver.probe = platform_drv_probe;
> if (drv->remove)
> @@ -539,12 +541,12 @@ int __init_or_module platform_driver_probe(struct platform_driver *drv,
> * if the probe was successful, and make sure any forced probes of
> * new devices fail.
> */
> - spin_lock(&platform_bus_type.p->klist_drivers.k_lock);
> + spin_lock(&drv->driver.bus->p->klist_drivers.k_lock);
> drv->probe = NULL;
> if (code == 0 && list_empty(&drv->driver.p->klist_devices.k_list))
> retval = -ENODEV;
> drv->driver.probe = platform_drv_probe_fail;
> - spin_unlock(&platform_bus_type.p->klist_drivers.k_lock);
> + spin_unlock(&drv->driver.bus->p->klist_drivers.k_lock);
>
> if (code != retval)
> platform_driver_unregister(drv);
> @@ -1017,6 +1019,26 @@ struct bus_type platform_bus_type = {
> };
> EXPORT_SYMBOL_GPL(platform_bus_type);
>
> +/** platform_bus_type_init - fill in a pseudo-platform-bus
> + * @bus: foriegn bus type
> + *
> + * This init is basically a selective memcpy that
> + * won't overwrite any user-defined attributes and
> + * only copies things that platform bus defines anyway
> + */
> +void platform_bus_type_init(struct bus_type *bus)
> +{
> + if (!bus->dev_attrs)
> + bus->dev_attrs = platform_bus_type.dev_attrs;
> + if (!bus->match)
> + bus->match = platform_bus_type.match;
> + if (!bus->uevent)
> + bus->uevent = platform_bus_type.uevent;
> + if (!bus->pm)
> + bus->pm = platform_bus_type.pm;
> +}
> +EXPORT_SYMBOL_GPL(platform_bus_type_init);
> +
> int __init platform_bus_init(void)
> {
> int error;
> diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h
> index 5417944..fa8c35a 100644
> --- a/include/linux/platform_device.h
> +++ b/include/linux/platform_device.h
> @@ -79,6 +79,8 @@ extern int platform_driver_probe(struct platform_driver *driver,
> #define platform_get_drvdata(_dev) dev_get_drvdata(&(_dev)->dev)
> #define platform_set_drvdata(_dev,data) dev_set_drvdata(&(_dev)->dev, (data))
>
> +extern void platform_bus_type_init(struct bus_type *);
> +
> extern struct platform_device *platform_create_bundle(struct platform_driver *driver,
> int (*probe)(struct platform_device *),
> struct resource *res, unsigned int n_res,
--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
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