linux-kernel - Re: [PATCH] usb: gadget: USB3 support to the legacy printer driver

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Message-ID: <20141119031405.GD24874@saruman>
Date:	Tue, 18 Nov 2014 21:14:05 -0600
From:	Felipe Balbi <balbi@...com>
To:	Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
CC:	<balbi@...com>, Greg KH <gregkh@...uxfoundation.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCH]  usb: gadget: USB3 support to the legacy printer driver

On Tue, Nov 18, 2014 at 04:33:42PM -0500, Jorge Ramirez-Ortiz wrote:
> On 11/18/2014 03:47 PM, Felipe Balbi wrote:
> > Hi,
> >
> > On Tue, Nov 18, 2014 at 03:41:43PM -0500, Jorge Ramirez-Ortiz wrote:
> >>>>> you have no clue what these mean, do you ? How about reading the USB
> >>>>> specification of even http://www.beyondlogic.org/usbnutshell/usb1.shtml
> >>>> Unfortunately I do.
> >>>> It was easier to temporarily hack the driver code for a test - while I
> >>>> was at it - rather than modifying the host code.
> >>>> Since you asked for them, I though you would read the logs and wonder
> >>>> where the funny ids where coming from.
> >>> why do you even need to hack the host driver for these ? The driver
> >>> shows a Printer Class interface and the linux host side driver should
> >>> bind to it without any issues.
> >> the hack was on the gadget side.
> >>
> >> the usbhost test code in charge of sending the file to the device had the wrong ids.
> >> to save time -since I was modifying the gadget driver code and only for the
> >> tests (it is not part of the final patch) - I hacked those ids on the printer.c
> >> file.
> >> but anyway. lets move on. I removed those, recompiled the usb host code and sent
> >> the new traces.
> > then the host side needs a fix because it shouldn't really care about
> > the device ID, rather it should care about the class being printer.
> 
> absolutely.
> however if you use libusb_open_device_with_vid_pid then well, these things happen...

heh :-)

> >>>> That hack above would have given you an answer: so I kind of know what
> >>>> the ids are for. honestly.  anyway, will send the new logs - it took
> >>>> me a while to find and modify the host test code.
> >>> Which host test code ? Why don't you just use lpr or even cat file >
> >>> /dev/lp0 or something like that ?
> >> it is some proprietary code that links libusb -part of a different project: it
> >> was useful as it generated some metrics I was interested in.
> > I would be surprised if lpr doesn't work for the same purpose.
> >
> >>>>> do you want to debug that and find the culprit since you're already at
> >>>>> it ?
> >>>> probably: I still need to get used to this process, thanks for bearing
> >>>> with me on this.
> >>> no problem.
> >>>
> >>>> I spoke to Ricardo Ribalda three months ago while I was doing this
> >>>> stuff.  but yes, I might work on this -after I finish with this
> >>>> patch!- since I have access to the hardware locally.
> >>> cool, that'll help.
> >> notice that the original PLX driver was still far from the theoretical 5Gbps
> >> target (I was expecting to measure at least 3Gbps and could only get 1Gbps).
> >> So 1Gbps should be the target to meet on the kernel.org net2280 - do you agree?
> > this depends on a whole bunch of things. Mainline is a lot different
> > from PLX's kernel tree, I'm sure.
> >
> > It also depends on how many PCIe lanes you're using. Just because USB3
> > guarantees 5Gbps bandwidth, if you use a 1x PCIe connector, you'll never
> > get that ;-)
> >
> 
> yes, that is why I purchased a Lenovo ThinkServer TS140 just for this
> integration.  it has one x16 Gen3 PCIe slot, one x1 Gen2 PCIe and one
> x16 Gen2 PCIe (x4 signal).  so this should be enough.

right, assuming PLX PCIe card actually supports that :-)

> on the host side, I have good server as well.  So really, there is no
> excuse to not get this right unless there is a problem in the plx
> silicon but from the Windows based metrics that I saw I dont think so.
> The only think I am missing is the USB3 analyzer I used to have in my
> previous company.

yeah, that helps a lot indeed. I'm always using my trusty beagle 5000.

-- 
balbi

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