Re: [REPOST][PATCH 2/2] driver core: platform: allow platform drivers to bind to any device

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Dec 03, 2013 at 12:34:54PM +0000, Kim Phillips wrote:
> Platform drivers such as the vfio-platform "meta-" driver [1]
> should be allowed to specify that they can bind to any device,
> much like PCI drivers can with PCI_ANY_ID.
> 
> Currently, binding platform drivers to devices depends on:
> 
> - a string match in the device node's compatible entry (OF)
> - a string match in the ACPI id list (ACPI)
> - a string match in the id_table (platform data)
> - a string match on the driver name (fall-back)
> 
> none of which allow for the notion of "match any."
> 
> This patch adds the notion by adding a "match any device" boolean to
> struct platform_driver, for drivers to be able to set and thus not cause
> platform_match() to fail when a bind is requested.
> 
> [1] http://www.spinics.net/lists/kvm/msg96701.html
> 
> Signed-off-by: Kim Phillips <kim.phillips@linaro.org>
> ---
> rebased onto 3.13-rc2, and reposted from first submission which
> received no comments:
> 
> https://lkml.org/lkml/2013/10/11/48
> 
>  drivers/base/platform.c         | 4 ++++
>  include/linux/platform_device.h | 1 +
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 3a94b79..78a5b62 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -736,6 +736,10 @@ static int platform_match(struct device *dev, struct device_driver *drv)
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct platform_driver *pdrv = to_platform_driver(drv);
>  
> +	/* the driver matches any device */
> +	if (pdrv->match_any_dev)
> +		return 1;

This breaks userspace in that it will never know to load the module that
can "bind to anything".

You need a way to encode this in the platform device id that can be a
wildcard type of thing, so that userspace can know about this.

thanks,

greg k-h