Date: Thu, 2 Jul 2020 12:37:47 +0200 From: Jan Behrens <jbe-mlist@magnetkern.de> To: Hans Petter Selasky <hps@selasky.org> Cc: "freebsd-usb@FreeBSD.org" <freebsd-usb@freebsd.org> Subject: Re: USB reset fails when using a LimeSDR Mini on FreeBSD Message-ID: <20200702123747.1bdf36b9d2ebe283f7bb855e@magnetkern.de> In-Reply-To: <8ac365f3-3d33-4730-622e-e66f29dd5938@selasky.org> References: <20200625121052.e9f7e7cbeb68fad264ec80a9@magnetkern.de> <5c0729f9-9e98-52f7-a5cb-6c5dfd2287a3@selasky.org> <20200626172851.872f3a08fa6e632666683230@magnetkern.de> <CAM8r67AF%2BfGiqBr9A0863Za_zR-fG1FxGfNAqEvvafW=wTRmyQ@mail.gmail.com> <20200627144419.f14371695d9b62ea99106c4a@magnetkern.de> <CAM8r67DTKdj0%2BhkOegjBj-ywzWFq2CnS2sQed0mibSUeGp6HSQ@mail.gmail.com> <20200627173604.7f7b7777140e66dbad812fc7@magnetkern.de> <CAM8r67DqZzje=JnrT_R3d6Uo_NxjvGsvpydd1NOTrJHU2jHzQA@mail.gmail.com> <20200627180420.4b8012fb@ernst.home> <20200702103523.adb0566bcc7b6e354905a8a5@magnetkern.de> <97c8fd11-9200-dff7-4c68-b0b80cc44871@selasky.org> <20200702104743.223e98c325806025704703f2@magnetkern.de> <e3bd0417-c89c-5598-448e-33ec1e505a3f@selasky.org> <20200702111538.e7edf0ae8d10ec7ede9acebb@magnetkern.de> <9e14575a-5c8b-28c8-6593-22019a21e7e7@selasky.org> <20200702120655.73d1111e2de81c626be78139@magnetkern.de> <8ac365f3-3d33-4730-622e-e66f29dd5938@selasky.org>
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On Thu, 2 Jul 2020 12:18:02 +0200 Hans Petter Selasky <hps@selasky.org> wrote: > Hi Jan, > > On 2020-07-02 12:06, Jan Behrens wrote: > > On Thu, 2 Jul 2020 11:23:32 +0200 > > Hans Petter Selasky <hps@selasky.org> wrote: > > > >> On 2020-07-02 11:15, Jan Behrens wrote: > >>> On Thu, 2 Jul 2020 10:54:27 +0200 > >>> Hans Petter Selasky <hps@selasky.org> wrote: > >>> > >>>> On 2020-07-02 10:47, Jan Behrens wrote: > >>>>> But wouldn't both drivers require access to the entries in /dev ? > >>>> > >>>> Yes, user-space drivers would require access to /dev, yes, but kernel > >>>> drivers not, like mouse, keyboard, storage, network. > >>>> > >>>> [...] > > > I experienced that /dev/usb/2.2.0 and /dev/usb/2.2.1, 2.2.2, 2.2.3, > > etc. get treated differently when I reset the LimeSDR Mini with > > "usbconfig -u 2 -a 2 reset". The devices 2.2.1 and up are supposingly > > re-created (and have their access rights reset), while the device 2.2.0 > > maintains any manually changed access rights. > > > > Let me explain, now you are getting me into dirty details :-) > > This device is used for all of LibUSB interfaces and gives access to all > endpoints: > > /dev/usb/X.Y.0 > > These devices are legacy devices, which allow direct access to the > endpoint via the shell. They are there to support the old user-space > model FreeBSD had. And they are re-created when you reset/reconfigure a > USB device. Actually you can "echo > /dev/usb/X.Y.N" to write directly > to an endpoint from user-space. But don't do that unless it is a modem > endpoint which support AT commands for example. > > /dev/usb/X.Y.[1..15] Are these devices there only for legacy reasons? Or also for granting access to devices via chown/chmod (or devfs.rules)? I see that /dev/ugenX.Y are symlinks to /dev/usb/X.Y.0 I used chown user /dev/usb/2.2.* to get access through libusb (before I set up devfs.rules). > > > Is it correct that 2.2.0 identifies the device as a whole? > > Yes, this is correct. Then I suppose if you have access to /dev/ugenX.Y (i.e. /dev/usb/X.Y. 0), you should be allowed to reset a device. > > >> > >> What do you think? > > > > I'm not sure if this is (from a semantic point of view) the best thing > > to do. I would say you should only be able to reset a device if you > > have been granted access to the device as a whole (including all > > interfaces/subdevices/whatever), as the reset seems to affect all of > > those. > > > > In FreeBSD and LibUSB there is no such concept. Everything is oriented > around interfaces. There is a function to claim an interface, but not > the device itself. (man libusb_claim_interface) That means in order to reset the device itself, I need to claim an interface, e.g. interface 0? But above you said, 2.2.0 identifies the device as a whole (and I noted it is symlinked by /dev/ugen2.2). So I'm a bit confused now. Is /dev/usb/2.2.0 the whole device? Or the interface 0 of the device? Or both... haha > [...] Regards, Jan
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