[v4,2/2] usb/gadget: Add driver for Aspeed SoC virtual hub

[Alan Stern <stern@rowland.harvard.edu>]

On Sat, 17 Mar 2018, Benjamin Herrenschmidt wrote:

> On Fri, 2018-03-16 at 16:56 -0400, Alan Stern wrote:
> > On Fri, 16 Mar 2018, Benjamin Herrenschmidt wrote:
> > 
> > > On Thu, 2018-03-15 at 08:03 +1100, Benjamin Herrenschmidt wrote:
> > > > > > Do you have more comments for the rest of the driver or that's it ?
> > > > > 
> > > > > so far, that's it.
> > > > 
> > > > Ok. I'll re-send.
> > > 
> > > So I'll resend in a minute, doing a few more tests, however, I've
> > > noticed something which I wont' have time to track down til at
> > > best next week, I wonder if it's normal/expected.
> > > 
> > > If I just create a mass storage function set to be "removable" and
> > > "cdrom" with no file attached,  and enable it, I get an endless stream
> > > of resets. It looks like the host constantly does USB resets.
> > 
> > That's not why I get.  There's an endless stream of messages, but it
> > doesn't include any resets.  Just command failures and endpoint halts.  
> > For example:
> 
>  .../...
> 
> In my case, I was getting resets on the host:
> 
> [383250.844611] usb 1-1: new high-speed USB device number 84 using xhci_hcd
> [383250.972235] usb 1-1: New USB device found, idVendor=1d6b, idProduct=0107
> [383250.972244] usb 1-1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
> [383250.972251] usb 1-1: Product: USB Virtual Hub
> [383250.972257] usb 1-1: Manufacturer: Aspeed
> [383250.972262] usb 1-1: SerialNumber: 00000000
> [383250.979127] hub 1-1:1.0: USB hub found
> [383250.979218] hub 1-1:1.0: 5 ports detected
> [383284.910195] usb 1-1.1: new high-speed USB device number 85 using xhci_hcd
> [383284.988326] usb 1-1.1: New USB device found, idVendor=1d6b, idProduct=0104
> [383284.988339] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> [383284.988349] usb 1-1.1: Product: Bar Gadget
> [383284.988358] usb 1-1.1: Manufacturer: Foo Inc.
> [383284.988366] usb 1-1.1: SerialNumber: 0123456789
> [383285.000159] usb-storage 1-1.1:1.0: USB Mass Storage device detected
> [383285.000613] scsi host3: usb-storage 1-1.1:1.0
> [383286.063152] scsi 3:0:0:0: CD-ROM            Linux    File-CD Gadget   0416 PQ: 0 ANSI: 2
> [383286.064148] sr 3:0:0:0: Power-on or device reset occurred
> [383286.129411] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383286.284397] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383286.438396] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383286.593487] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383286.676863] sr 3:0:0:0: [sr0] scsi-1 drive
> [383286.676871] cdrom: Uniform CD-ROM driver Revision: 3.20
> [383286.678558] sr 3:0:0:0: Attached scsi CD-ROM sr0
> [383286.679426] sr 3:0:0:0: Attached scsi generic sg2 type 5
> [383286.746343] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383286.901458] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.056423] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.211445] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.360422] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.516295] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.671464] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.827423] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> [383287.912048] sr 3:0:0:0: Power-on or device reset occurred
> [383288.013376] usb 1-1.1: reset high-speed USB device number 85 using xhci_hcd
> 
> The guest just show config selection messages. I'll dig a bit next week
> in case there's an issue with my UDC driver there.

Output from usbmon could help.

> As for ...
> 
> > It's worth pointing out that all those messages are at DEBUG level.  
> > Although they fill up the kernel's log buffer, they won't be noticeable 
> > to most users.
> > 
> > In any case, g-mass-storage was never intended be a complete emulation 
> > of a CD or DVD drive.  Its support for those modes is minimal; it was 
> > originally intended just to emulate a hard disk drive.
> 
> Then it will be worthwhile me or somebody else spending a bit of time
> beefing it up a little bit. I'll see if I can spare time in the next
> couple of weeks.

Maybe...  Even after cdrom support was added to the gadget, the scope 
was limited.  It was intended to emulate _only_ a CD drive, not a DVD 
drive.

Also, if I'm not mistaken, the commands that the emulation doesn't 
handle are all optional.

Alan Stern

> The Aspeed chip is a BMC chip, ie server management processor, and is
> connected via the USB gadget to the actual server (the host). One of
> the usage scenario here is to use USB gadget to present distro ISOs as
> USB CD/DVDs to the host for remote provisioning (sourced over the
> network via something like nbd).
> 
> Note that due to the limitation of having to use a file or a block
> device, we might end up doing a userspace CDROM emulation instead that
> can source ISOs via things like HTTPS instead, but initially the above
> is what we are toying with.
> 
> Cheers,
> Ben.
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