Re: [PATCH] usb: acpi: Fix shifting 31 bits

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Mar 17, 2021 at 10:25:13PM +0800, jzp0409 wrote:
> From: "edison.jiang" <jiangzhipeng@yulong.com>
> 
> Fix undefined behaviour in the usb apci driver by using 'BIT' marcro.

What is undefined about it?

> 
> Signed-off-by: edison.jiang <jiangzhipeng@yulong.com>

This name is not a valid signed-off-by name (I doubt you sign documents
with a ".", right?) and it does not match the "From:" name either, so
something needs to be fixed before this patch could be accepted.

> ---
>  drivers/usb/core/usb-acpi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/usb-acpi.c b/drivers/usb/core/usb-acpi.c
> index 50b2fc7..3e467a8 100644
> --- a/drivers/usb/core/usb-acpi.c
> +++ b/drivers/usb/core/usb-acpi.c
> @@ -122,7 +122,7 @@ static enum usb_port_connect_type usb_acpi_get_connect_type(acpi_handle handle,
>   * Private to usb-acpi, all the core needs to know is that
>   * port_dev->location is non-zero when it has been set by the firmware.
>   */
> -#define USB_ACPI_LOCATION_VALID (1 << 31)
> +#define USB_ACPI_LOCATION_VALID BIT(31)

I do not understand what this is trying to fix, please be more specific.

thanks,

greg k-h