Re: [PATCH] driver-core: remove lock for platform devices during probe

[Greg Kroah-Hartman]

On Mon, Apr 24, 2017 at 01:42:16PM +0800, Wei Li wrote:
> During driver probe procedure, lock on the parent of
> platform devices could be removed to make probe in
> parallel.
> 
> Signed-off-by: Wei Li <weili@xxxxxxxxxxxxxx>

Why?  Why does this matter?

> ---
>  drivers/base/dd.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index a1fbf55..e238fbc 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -25,6 +25,7 @@
>  #include <linux/async.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/pinctrl/devinfo.h>
> +#include <linux/platform_device.h>
>  
>  #include "base.h"
>  #include "power/power.h"
> @@ -749,13 +750,14 @@ static int __driver_attach(struct device *dev, void *data)
>  		return ret;
>  	} /* ret > 0 means positive match */
>  
> -	if (dev->parent)	/* Needed for USB */
> +	if (dev->parent &&
> +		(dev->bus != &platform_bus_type))	/* Needed for USB */

The platform_bus_type check is not needed by USB, right?

thanks,

greg k-h