[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RFC v1] libxl: Introduce a template for devices with a controller
On Wed, 2015-06-17 at 13:28 +0200, Juergen Gross wrote: > On 06/17/2015 01:06 PM, Ian Campbell wrote: > > On Thu, 2015-05-21 at 18:07 +0100, George Dunlap wrote: > >> We have several outstanding patch series which add devices that have > >> two levels: a controller and individual devices attached to that > >> controller. > >> > >> In the interest of consistency, this patch introduces a section that > >> sketches out a template for interfaces for such devices. > > > > Chun Yan and Jeurgen: > > > > I was hoping we could come to some sort of agreement on this such that > > it can be used as the basis for both the pvusb and pvscsi interfaces. As > > such your feedback here is important... > > I already gave some feedback. As everything regarding this feedback > has been discussed: > > Acked-by: Juergen Gross <jgross@xxxxxxxx> Actually, maybe I really meant to ping Olaf instead/as well since he's doing the libxl side of pvscsi (you're doing the driver upstreaming, right?). So, Olaf, ping... > > > > >> > >> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> > >> --- > >> CC: Ian Campbell <ian.campbell@xxxxxxxxxx> > >> CC: Ian Jackson <ian.jackson@xxxxxxxxxx> > >> CC: Wei Liu <wei.liu2@xxxxxxxxxx> > >> CC: Juergen Gross <jgross@xxxxxxxx> > >> CC: Chun Yan Liu <cyliu@xxxxxxxx> > >> CC: Olaf Hering <olaf@xxxxxxxxx> > >> > >> So, this is definitely RFC -- I tried to spec things out in a way that > >> made sense, but I often just chose something that I thought would be a > >> sensible starting point for discussion. > >> > >> This spec looks a lot more like the PVUSB spec than the PVSCSI spec, > >> in part because I think the PVUSB spec has already had a lot more > >> thought that's gone into it. > >> > >> A couple of random points to discuss: > >> > >> * Calling things "controllers", using <type>ctrl for the device name, > >> and using "ctrl" as the field name for the devid of the controller > >> in the individual devices. > >> > >> * I've said that having an index (port, lun, whatever) is optional. > >> Do we want to make that requred? Do we want it to have a consistent > >> name? In the case of emulated USB, we can't really specify to qemu > >> what port the device gets attached to, so I'm tempted to say it's > >> not required; but even there we could always give it a port number > >> just for name's sake. > >> > >> * Naming sub-devices. We need to have a way to uniquely name both > >> controllers and subdevices. Here I've said that we will have both > >> <type>ctrl and <type> devid namespaces, mainly because in the > >> previous point I opted not to require an index. Another option > >> would be not to have another devid namespace, but to use > >> <ctrl,index> as the unique identifier. (This would mean requiring > >> the index/port/lun specification above.) > >> > >> * libxl_device_<type>_list listing devices across all controllers. I > >> think this is the most practical thing to do, but one could imagine > >> wanting to query by controller ID instead. > >> > >> Feedback welcome. > >> --- > >> tools/libxl/libxl.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > >> 1 file changed, 46 insertions(+) > >> > >> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h > >> index 2ed7194..d757845 100644 > >> --- a/tools/libxl/libxl.h > >> +++ b/tools/libxl/libxl.h > >> @@ -1234,6 +1234,52 @@ void libxl_vtpminfo_list_free(libxl_vtpminfo *, int > >> nr_vtpms); > >> * > >> * This function does not interact with the guest and therefore > >> * cannot block on the guest. > >> + * > >> + * Controllers > >> + * ----------- > >> + * > >> + * Most devices are treated individually. Some devices however, like > >> + * USB or SCSI, inherently have the need to have "busses" or > >> + * "controllers" to which individual devices can be attached. > >> + * > >> + * In that case, for each <type>, there will be two sets of the > >> + * functions, types, and devid namespaces outlined above: one based on > >> + * '<type>', and one based on '<type>ctrl'. > >> + * > >> + * In those cases, libxl_device_<type>ctrl_<function> will act more or > >> + * less like top-level non-bus devices: they will either create or > >> + * accept a libxl_devid which will be unique within the > >> + * <type>ctrl libxl_devid namespace. > >> + * > >> + * Second-level devices which will be attached to a controller will > >> + * include in their libxl_device_<type> a field called ctrl, which > >> + * will be the libxl_devid of the corresponding controller. It may also > >> + * include an index onto that bus, that represents (for example) a USB > >> + * port or a SCSI LUN. > >> + * > >> + * These second-level devices will also have their own devid which > >> + * will be unique within the <type> devid namespace, and will be used > >> + * for queries or removals. > >> + * > >> + * In the case where there are multiple different ways to implement a > >> + * given device -- for instance, one which is fully PV and one which > >> + * uses an emulator -- the controller will contain a field which > >> + * specifies what type of implementation is used. The implementations > >> + * of individual devices will be known by the controller to which they are > >> + * attached. > >> + * > >> + * If libxl_device_<type>_add receives an uninitialized ctrl devid, it > >> + * may return an error. Or it may (but is not required to) choose to > >> + * automatically choose a suitable controller to which to attach the > >> + * new device. It may also (but is not required to) automatically > >> + * create a new controller if no suitable controllers exist. > >> + * Individual devices should document their behavior. > >> + * > >> + * libxl_device_<type>ctrl_list will list all controllers for the domain. > >> + * > >> + * libxl_device_<type>_list will list all devices for all controllers > >> + * for the domain. The individual libxl_device_<type> will include > >> + * the devid of the controller to which it is attached. > >> */ > >> > >> /* Disks */ > > > > > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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