From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:35130 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753617Ab1GOXmN (ORCPT ); Fri, 15 Jul 2011 19:42:13 -0400 Message-ID: <4E20D042.3000302@iki.fi> Date: Sat, 16 Jul 2011 02:41:54 +0300 From: Antti Palosaari MIME-Version: 1.0 To: Andreas Oberritter CC: Mauro Carvalho Chehab , Ralph Metzler , linux-media@vger.kernel.org Subject: Re: [PATCH 0/5] Driver support for cards based on Digital Devices bridge (ddbridge) References: <201107032321.46092@orion.escape-edv.de> <4E1F8E1F.3000008@redhat.com> <4E1FBA6F.10509@redhat.com> <201107150717.08944@orion.escape-edv.de> <19999.63914.990114.26990@morden.metzler> <4E203FD0.4030503@redhat.com> <4E207252.5050506@linuxtv.org> In-Reply-To: <4E207252.5050506@linuxtv.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 07/15/2011 08:01 PM, Andreas Oberritter wrote: > 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. One thing I want to say is that consider about devices which does have MFE using two different *physical* demods, not integrated to same silicon. If you add such FE delsys switch mechanism it needs some more glue to bind two physical FEs to one virtual FE. I see much easier to keep all FEs as own - just register those under the same adapter if FEs are shared. regards Antti -- http://palosaari.fi/