On 15.07.2011 15:25, Mauro Carvalho Chehab wrote: > Em 15-07-2011 05:26, Ralph Metzler escreveu: >> At the same time I want to add delivery system properties to >> support everything in one frontend device. >> Adding a parameter to select C or T as default should help in most >> cases where the application does not support switching yet. > > If I understood well, creating a multi-delivery type of frontend for > devices like DRX-K makes sense for me. > > We need to take some care about how to add support for them, to avoid > breaking userspace, or to follow kernel deprecating rules, by adding > some legacy compatibility glue for a few kernel versions. So, the sooner > we add such support, the better, as less drivers will need to support > a "fallback" mechanism. > > The current DVB version 5 API doesn't prevent some userspace application > to change the delivery system[1] for a given frontend. This feature is > actually used by DVB-T2 and DVB-S2 drivers. This actually improved the > DVB API multi-fe support, by avoiding the need of create of a secondary > frontend for T2/S2. > > Userspace applications can detect that feature by using FE_CAN_2G_MODULATION > flag, but this mechanism doesn't allow other types of changes like > from/to DVB-T/DVB-C or from/to DVB-T/ISDB-T. So, drivers that allow such > type of delivery system switch, using the same chip ended by needing to > add two frontends. > > Maybe we can add a generic FE_CAN_MULTI_DELIVERY flag to fe_caps_t, and > add a way to query the type of delivery systems supported by a driver. > > [1] http://linuxtv.org/downloads/v4l-dvb-apis/FE_GET_SET_PROPERTY.html#DTV-DELIVERY-SYSTEM I don't think it's necessary to add a new flag. It should be sufficient to add a property like "DTV_SUPPORTED_DELIVERY_SYSTEMS", which should be read-only and return an array of type fe_delivery_system_t. Querying this new property on present kernels hopefully fails with a non-zero return code. in which case FE_GET_INFO should be used to query the delivery system. In future kernels we can provide a default implementation, returning exactly one fe_delivery_system_t for unported drivers. Other drivers should be able to override this default implementation in their get_property callback. Regards, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
