From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oneukum@suse.com>
Cc: gregkh@lnuxfoundation.org, linux-usb@vger.kernel.org
Subject: Re: [PATCHv2] usb: usb_parse_endpoint ignore reserved bits
Date: Thu, 18 Apr 2024 11:51:21 -0400 [thread overview]
Message-ID: <27b5e66d-b2d7-45dd-85f2-3d06757493de@rowland.harvard.edu> (raw)
In-Reply-To: <20240418110249.10643-1-oneukum@suse.com>
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
> ---
> 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;
See my earlier reply. The 0x0f here should be USB_ENDPOINT_NUMBER_MASK.
Or even better, you could use the usb_endpoint_num() inline routine.
> + 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 the common control endpoint, skipping\n",
"endpoint 0" would be simpler than "the common control endpoint".
Alan Stern
> + cfgno, inum, asnum);
> goto skip_to_next_endpoint_or_interface_descriptor;
> }
>
> --
> 2.44.0
>
prev parent reply other threads:[~2024-04-18 15:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 11:02 [PATCHv2] usb: usb_parse_endpoint ignore reserved bits Oliver Neukum
2024-04-18 13:00 ` Greg KH
2024-04-18 15:51 ` Alan Stern [this message]
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