Re: [Xen-devel] [PATCH V8 3/7] libxl: add pvusb API

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 19/11/15 06:24, Chun Yan Liu wrote:
> 
> 
>>>> On 11/19/2015 at 09:33 AM, in message
> <564D97610200006600085301@xxxxxxxxxxxxxxxxxxxxxxx>, "Chun Yan Liu"
> <cyliu@xxxxxxxx> wrote: 
> 
>>  
>>>>> On 11/18/2015 at 05:44 PM, in message <20151118094410.GB21970@xxxxxxxxx>, 
>>>>> Olaf 
>> Hering <olaf@xxxxxxxxx> wrote:  
>>> On Tue, Nov 17, Chun Yan Liu wrote:  
>>>   
>>>> I think libxl_device_usb doesn't need to be changed into   
>>> libxl_device_usbdev?   
> 
> George & Olaf,
> 
> About the naming, can we get to a decision?
> e.g.
> * usb controller and everything related, using "usbctrl"
> * usb device and everything related, using "usbdev" (?)
> Currently in pvusb, almost everywhere referring to a usb device, we use "usb".
> Like: libxl_device_usb, libxl_device_usb_add/remove, etc.
> 
> If we decide, I can update all together.

So I finally went back and spent some time mulling over the e-mail
thread we had before about designing the interface.

Just as a reminder, SCSI has a topology of host / bus / target / LUN;
USB has a topology controller / hub[bus] / [port]device / interface.

At the moment in USB we're not dealing with virtual hubs, so each
controller will have a single bus.  Additionally, we are only passing
through and/or creating devices; a physical device with more than one
interface will have all of its interfaces passed through transparently.
 So we're only effectively exposing two levels in our API.

In the previous discussion, for pvscsi, Juergen argued it makes sense to
be able to assign LUNs from the same physical target to different
virtual targets; and it also makes sense to be able to assign
newly-created physical LUNs to existing virtual targets.

(Please people correct me if I've misunderstood something anywhere.)

So for SCSI, there may be three levels at which people want to be able
to do things.

Given, that, I wonder if it would make sense to name the different
"levels" for these multi-level devices after the name for that level in
their respective specificaitons.

I.e., libxl_device_usbctrl, libxl_device_usbdev, libxl_device_scsihost,
libxl_device_scsitgt, libxl_device_scsilun or something like that.

In which case, "usbdev" would be indicated (since it's the "device"
we're talking about).

Thoughts?

 -George

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