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Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers.

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Alan Stern <stern@rowland.harvard.edu> writes:
> On Mon, 25 Jan 2016, Bjørn Mork wrote:
>
>> I don't feel much like an expert here, but I can certainly make up an
>> opinion anyway :)
>> 
>> Since 64bits kernels allow usb devio with interface numbers up to 63, I
>> guess you need __u64 to avoid limiting the range?  Limiting will create
>> all sorts of followup problems, so it's definitely easiest to just go
>> with __u64.
>
> But the Linux USB stack only allows up to 32 interfaces (see
> include/linux/usb.h):
>
> /* this maximum is arbitrary */
> #define USB_MAXINTERFACES	32


Ah, I totally missed that.  Thanks


> So there's no point using a 64-bit value.
>
> On the other hand, this value is supposed to be the same size as 
> ps->ifclaimed, which is used as an argument to clear_bit(), set_bit(), 
> and test_bit().  Those routines require unsigned long.

Maybe the input to these should be clamped to USB_MAXINTERFACES?


Bjørn

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Re: [PATCH v1 0/1] ioctl to disallow detaching kernel USB drivers Emilio López <emilio.lopez@collabora.co.uk> - 2016-01-19 17:50 +0100
  Re: [PATCH v1 0/1] ioctl to disallow detaching kernel USB drivers Greg KH <gregkh@linuxfoundation.org> - 2016-01-19 19:10 +0100
    [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers. Emilio López <emilio.lopez@collabora.co.uk> - 2016-01-22 01:00 +0100
      Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers. Bjørn Mork <bjorn@mork.no> - 2016-01-22 10:50 +0100
        Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB  drivers. Emilio López <emilio.lopez@collabora.co.uk> - 2016-01-25 03:10 +0100
          Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers. Bjørn Mork <bjorn@mork.no> - 2016-01-25 09:50 +0100
            Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel  USB drivers. Alan Stern <stern@rowland.harvard.edu> - 2016-01-25 16:30 +0100
              Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers. Bjørn Mork <bjorn@mork.no> - 2016-01-25 16:40 +0100
                Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel  USB drivers. Alan Stern <stern@rowland.harvard.edu> - 2016-01-25 16:50 +0100
      Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel  USB drivers. Alan Stern <stern@rowland.harvard.edu> - 2016-01-22 17:20 +0100
        Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB  drivers. Emilio López <emilio.lopez@collabora.co.uk> - 2016-01-25 03:10 +0100

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