Re: [PATCHv2] usb: usb_parse_endpoint ignore reserved bits

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Apr 18, 2024 at 01:02:21PM +0200, Oliver Neukum wrote:
> Reading bEndpointAddress the spec tells is
> that
> 
> b7 is direction, which must be ignored
> b6:4 are reserved which are to be set to zero
> b3:0 are the endpoint address
> 
> In order to be backwards compatible with possible
> future versions of USB we have to be ready with
> devices using those bits. That means that we
> also have to ignore them like we do with the direction
> bit.
> In consequence the only illegal address you can
> encoding in four bits is endpoint zero, for which
> no descriptor must exist. Hence the check for exceeding
> the upper limit on endpoint addresses is removed.
> 
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> 
> V2: Improved commit log

Nit, "V2" goes below the --- line.

> ---
>  drivers/usb/core/config.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 8fd4208d17db..43c5ed256e6e 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -285,11 +285,11 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno,
>  		goto skip_to_next_endpoint_or_interface_descriptor;
>  	}
>  
> -	i = d->bEndpointAddress & ~USB_ENDPOINT_DIR_MASK;
> -	if (i >= 16 || i == 0) {
> +	i = d->bEndpointAddress & 0x0f;

Using a #define here instead of 0x0f might be good, right?

thanks,

greg k-h