Messages in this thread | | | Date | Mon, 25 Jan 2016 10:21:21 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers. |
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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
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.
Alan Stern
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