[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] libxl: Introduce a template for devices with a controller
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> --- 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" + * to higher-level ones. USB for instance has "controllers" at the + * top, which have busses, on which are devices, which consist of + * 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 + * 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 */ -- 2.1.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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