linux-kernel - Re: [PATCH] USB: add usbfs ioctl to get specific superspeedplus rates

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAGjSPUCQ892adFdYm7zCuMpWujwzwoQtYimvp3xXrnnCCyN47w@mail.gmail.com>
Date:   Wed, 26 Jul 2023 09:37:01 +0800
From:   Xiaofan Chen <xiaofanc@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Oliver Neukum <oneukum@...e.com>, Dingyan Li <18500469033@....com>,
        stern@...land.harvard.edu, sebastian.reichel@...labora.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: add usbfs ioctl to get specific superspeedplus rates

On Tue, Jul 25, 2023 at 10:23 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Mon, Jul 24, 2023 at 11:47:49AM +0200, Oliver Neukum wrote:
> > On 21.07.23 16:51, Greg KH wrote:
>> ...
> > > > 4. I found in libusb, there are two ways to get speed value for a device.
> > > >      One way is via sysfs, which has supported 20Gbps now. Another way is
> > > >      to use ioctl USBDEVFS_GET_SPEED. This is when I found this ioctl can only
> > > >      return USB_SPEED_SUPER_PLUS at most, it cannot determine current ssp rate
> > > >      further, no matter Gen1x2(10Gbps), Gen2x1(10Gbps) or Gen2x2(20Gbps). So I
> > > >      thought maybe it's good to provide a similar way like ioctl USBDEVFS_GET_SPEED
> > > >      in order to get ssp rates.
> > >
> > > If libusb doesn't need this ioctl, who would use it?  We only add apis
> > > that are actually going to be used.
> > >
> > > So if libusb doesn't use it, we need a real-world user for us to be able
> > > to add this.
> >
> > I am sorry, but that looks pretty much like a question of API design to me.
> > To what extent is libusb supposed to be functional without sysfs? There is
> > no technical answer to this. It is a question of design goals.
> >
> > If we follow the precedent of c01b244ad848a
> > ("USB: add usbfs ioctl to retrieve the connection speed")
> > then we should apply an updated version of Dingyan Li's patch, preferably
> > coupled with a patch for libusb or we go and deprecate some ioctls.
>
> We can never "deprecate" ioctls, sorry.
>
> So unless there is some actual need from userspace tools like libusb (or
> anything else?) that requires this new ioctl, let's not add it otherwise
> we are signing ourselves up to support it for forever.

Interestingly there is PR in libusb now, which uses sysfs for 20Gbps.
Maybe this new usbfs IOCTL is indeed good to have if we can not extend
the existing IOCTL USBDEVFS_GET_SPEED (but why not?).
https://github.com/libusb/libusb/pull/1298


-- 
Xiaofan