Date: Sun, 9 Nov 2008 17:48:05 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: Rink Springer <rink@freebsd.org> Cc: usb@freebsd.org, freebsd-usb@freebsd.org Subject: Re: Patch to convert usb2 to use cdev Message-ID: <200811091748.05863.hselasky@c2i.net> In-Reply-To: <20081109162835.GE78524@rink.nu> References: <20081109120257.GA78524@rink.nu> <200811091700.06932.hselasky@c2i.net> <20081109162835.GE78524@rink.nu>
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On Sunday 09 November 2008, Rink Springer wrote:
> Hi Hans,
>
> On Sun, Nov 09, 2008 at 05:00:05PM +0100, Hans Petter Selasky wrote:
> > It is not the same endpoint, but multiple different endpoints on the same
> > device through the same file handle. Instead of one endpoint per file,
> > you have one file handle for each set of endpoints you need for your USB
> > userland driver, like LibUSB. Then there is only one file-handle to poll.
> > Actually there are two modes in UGEN now. Maybe you were not aware. Let
> > me quickly explain:
> >
> > 1) Simple read/write mode that works with cat & dd.
> >
> > 2) Special USB FS mode which exposes the full USB features to userland.
> > This mode does not use read/write, but rather copyin, copyout and a set
> > of software USB descriptors.
>
> Hmm, I think I see what you mean. Basically, you just
> open("/dev/ugenX.Y") and you can use the USB_FS_xxx ioctl's to have
> fine-grained control. However, if you open("/dev/ugen.X.Y.Z"), you'd
> talk with endpoint Z on USB device X.Y.. this is actually quite cool,
> guess I should have studied usb2_generic.c more :-)
That's correct.
>
> I think it makes sense to say that if /dev/ugenX.Y is opened, you
> shouldn't be able to open /dev/ugenX.Y.Z, right? However, what happends
> if /dev/ugenX.Y.Z is opened? I'd think that opening /dev/ugenX.Y would
> be fine, but any ioctl() dealing with the corresponding endpoint Z
> should be denied.
I would say it be allowed to open the endpoint both ways at the same time. It
can make debugging easier.
But there can be two different processes opening /dev/ugenX.Y at the same
time, accessing different endpoints!
--HPS
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