[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] libxl: Introduce a template for devices with a controller
On 24/11/15 15:40, 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. > > Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx> Some typos (see below), otherwise: Acked-by: Juergen Gross <jgross@xxxxxxxx> > --- > 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> > > Changes in v1 (since the RFC): > > - Use <class> rather than <type>, and <level> rather than specifying > controller and device. The idea being to allow SCSI to use > terminology more natural to it (i.e., scsihost, scsitarget, scsilun) > rather than naming things after USB (controller & device). > > - Do not require each <level> to have a deviceid, but just a unique > naming schema. > > - Allow multiple levels. > > - Include the paragraph about domain configuration lists. > --- > tools/libxl/libxl.h | 65 > +++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 65 insertions(+) > > diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h > index 6b73848..46bcfe8 100644 > --- a/tools/libxl/libxl.h > +++ b/tools/libxl/libxl.h > @@ -1396,6 +1396,71 @@ 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 classes of device, > + * however, like USB or SCSI, inherently have the need to have a > + * heiarchy of different levels, with lower-level devices "attached" hierarchy > + * to higher-level ones. USB for instance has "controllers" at the > + * top, which have busses, on which are devices, which consist of buses? > + * multiple interfaces. SCSI has "hosts" at the top, then busses, > + * targets, and LUNs. > + * > + * In that case, for each <class>, there will be a set of funcitons functions > + * and types for each <level>. For example, for <class>=usb, there > + * may be <levels> ctrl (controller) and dev (device), with ctrl being > + * level 0. > + * > + * libxl_device_<class><level0>_<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><level0> libxl_devid namespace. > + * > + * Lower-level devices must have a unique way to be identified. One > + * way to do this would be to name it via the name of the next level > + * up plus an index; for instance, <ctrl devid, port number>. Another > + * way would be to have another devid namespace for that level. This > + * identifier will be used for queries and removals. > + * > + * Lower-level devices will will include in their > + * libxl_device_<class><level> struct a field referring to the unique > + * index of the level above. For instance, libxl_device_usbdev might > + * contain the controller devid. > + * > + * 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_<class><level>_add receives an empty reference to > + * the level above, it may return an error. Or it may (but is not > + * required to) automatically choose a suitable device in the level > + * above to which to attach the new device at this level. It may also > + * (but is not required to) automatically create a new device at the > + * level above if no suitable devices exist. Each class should > + * document its behavior. > + * > + * libxl_device_<class><level>_list will list all devices of <class> > + * at <level> in the domain. For example, libxl_class_usbctrl_list > + * will list all usb controllers; libxl_class_usbdev_list will list > + * all usb devices across all controllers. > + * > + * For each class, the domain config file will contain a single list > + * for each level. libxl will first iterate through the list of > + * top-level devices, then iterate through each level down in turn, > + * adding devices to devices in the level above. For instance, there > + * will be one list for all usb controllers, and one list for all usb > + * devices. > + * > + * If libxl_device_<class><level>_add automatically creates > + * higher-level devices as necessary, then it is permissible for the > + * higher-level lists to be empty and the device list to have devices > + * with the field containing a reference to the higher level device > + * uninitialized. > */ > > /* Disks */ > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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