From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oneukum@suse.com>
Cc: linux-usb@vger.kernel.org, gregKH@linuxfoundation.org
Subject: Re: [PATCHv3] usb: usb_parse_endpoint ignore reserved bits
Date: Thu, 2 May 2024 10:00:03 -0400 [thread overview]
Message-ID: <ad307bb5-d48a-4319-9cbf-205faf1c460b@rowland.harvard.edu> (raw)
In-Reply-To: <20240502115259.31076-1-oneukum@suse.com>
On Thu, May 02, 2024 at 01:51:40PM +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>
> ---
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
> v2: Improved commit log
> v3: Symbolic mask and improved error message
> 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 7f8d33f92ddb..3362af165ef5 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -279,11 +279,11 @@ 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 & USB_ENDPOINT_NUMBER_MASK;
> + if (i == 0) {
> dev_notice(ddev, "config %d interface %d altsetting %d has an "
> - "invalid endpoint with address 0x%X, skipping\n",
> - cfgno, inum, asnum, d->bEndpointAddress);
> + "invalid descriptor for endpoint zero, skipping\n",
> + cfgno, inum, asnum);
> goto skip_to_next_endpoint_or_interface_descriptor;
> }
>
> --
> 2.44.0
>
prev parent reply other threads:[~2024-05-02 14:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-02 11:51 [PATCHv3] usb: usb_parse_endpoint ignore reserved bits Oliver Neukum
2024-05-02 14:00 ` Alan Stern [this message]
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