Am Mittwoch, den 02.09.2009, 00:32 -0400 schrieb Michael Krufky: > Over the course of the past year, a number of developers have > expressed a need for giving the bridge drivers better control over > dvb_frontend operations. Specifically, there is a need for the bridge > driver to receive a DVB frontend IOCTL and have the opportunity to > allow or deny the IOCTL to proceed, as resources permit. > > For instance, in the case of a hybrid device, only the bridge driver > knows whether the analog functionality is presently being used. If > the driver is currently in analog mode, serving video frames, the > driver will have a chance to deny the DVB frontend ioctl request > before dvb-core passes the request on to the frontend driver, > potentially damaging the analog video stream already in progress. > > In some cases, the bridge driver might have to perform a setup > operation to use a feature specific to the device. For instance, the > bridge device may be in a low powered state - this new capability > allows the driver to wake up before passing the command on to the > frontend driver. This new feature will allow LinuxTV developers to > finally get working on actual power management support within the > v4l/dvb subsystem, without the fear of breaking devices with hybrid > analog / digital functionality. > > In other cases, there may be situations in which multiple RF > connectors are available to the tuner, but only the bridge driver will > be aware of this, as this type of thing is specific to the device's > hardware implementation. As there are many tuners capable of multiple > RF spigots, not all devices actually employ this feature - only the > bridge driver knows what implementations support such features, and > how to enable / disable them. > > The possibilities are endless. I actually did all the heavy lifting > involved in this a few months ago, but haven't had a moment to write > up this RFC until now. > > The change to dvb-core that allows this new functionality is posted to > my development repository on kernellabs.com. I have also included an > example of how this can be used on a digital tuner board with multiple > RF inputs. The multiple RF input switching is already supported in > today's code, but I promised Mauro that I would present a better > method of doing this before the upcoming merge window. For your > review and comments, please take a look at the topmost changesets, > starting with "create a standard method for dvb adapter drivers to > override frontend ioctls": > > http://kernellabs.com/hg/~mkrufky/fe_ioctl_override > > For those that would prefer not to open up a web browser, here are the > core changes (apologies if whitespace becomes broken): > > --- a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c Tue Jun 16 > 16:08:17 2009 -0400 > +++ b/linux/drivers/media/dvb/dvb-core/dvb_frontend.c Sat May 23 > 17:00:59 2009 -0400 > @@ -1594,7 +1594,18 @@ > struct dvb_device *dvbdev = file->private_data; > struct dvb_frontend *fe = dvbdev->priv; > struct dvb_frontend_private *fepriv = fe->frontend_priv; > - int err = -EOPNOTSUPP; > + int cb_err, err = -EOPNOTSUPP; > + > + if (fe->dvb->fe_ioctl_override) { > + cb_err = fe->dvb->fe_ioctl_override(fe, cmd, parg, > + DVB_FE_IOCTL_PRE); > + if (cb_err < 0) > + return cb_err; > + if (cb_err > 0) > + return 0; > + /* fe_ioctl_override returning 0 allows > + * dvb-core to continue handling the ioctl */ > + } > > switch (cmd) { > case FE_GET_INFO: { > @@ -1858,6 +1869,13 @@ > err = 0; > break; > }; > + > + if (fe->dvb->fe_ioctl_override) { > + cb_err = fe->dvb->fe_ioctl_override(fe, cmd, parg, > + DVB_FE_IOCTL_POST); > + if (cb_err < 0) > + return cb_err; > + } > > return err; > } > --- a/linux/drivers/media/dvb/dvb-core/dvbdev.h Tue Jun 16 16:08:17 > 2009 -0400 > +++ b/linux/drivers/media/dvb/dvb-core/dvbdev.h Sat May 23 17:00:59 > 2009 -0400 > @@ -51,6 +51,8 @@ > module_param_array(adapter_nr, short, NULL, 0444); \ > MODULE_PARM_DESC(adapter_nr, "DVB adapter numbers") > > +struct dvb_frontend; > + > struct dvb_adapter { > int num; > struct list_head list_head; > @@ -66,6 +68,32 @@ > int mfe_shared; /* indicates mutually exclusive > frontends */ > struct dvb_device *mfe_dvbdev; /* frontend device in use */ > struct mutex mfe_lock; /* access lock for thread creation */ > + > + /* Allow the adapter/bridge driver to perform an action before and/or > + * after the core handles an ioctl: > + * > + * DVB_FE_IOCTL_PRE indicates that the ioctl has not yet been handled. > + * DVB_FE_IOCTL_POST indicates that the ioctl has been handled. > + * > + * When DVB_FE_IOCTL_PRE is passed to the callback as the stage arg: > + * > + * return 0 to allow dvb-core to handle the ioctl. > + * return a positive int to prevent dvb-core from handling the ioctl, > + * and exit without error. > + * return a negative int to prevent dvb-core from handling the ioctl, > + * and return that value as an error. > + * > + * When DVB_FE_IOCTL_POST is passed to the callback as the stage arg: > + * > + * return 0 to allow the dvb_frontend ioctl handler to exit normally. > + * return a negative int to cause the dvb_frontend ioctl handler to > + * return that value as an error. > + */ > +#define DVB_FE_IOCTL_PRE 0 > +#define DVB_FE_IOCTL_POST 1 > + int (*fe_ioctl_override)(struct dvb_frontend *fe, > + unsigned int cmd, void *parg, > + unsigned int stage); > }; > > > > > > As you can see from the changeset, this allows the bridge to assert > control both before and after the frontend driver itself handles the > operation. Depending on the value returned by the bridge driver, > dvb-core can exit with error, proceed unchanged, or exit without > error. > > In order to allow some drivers to use the new feature, I had to make a > small change to videobuf-dvb: > > --- a/linux/drivers/media/video/videobuf-dvb.c Tue Jun 16 16:08:17 > 2009 -0400 > +++ b/linux/drivers/media/video/videobuf-dvb.c Sat May 23 17:00:59 > 2009 -0400 > @@ -144,7 +144,9 @@ > struct device *device, > char *adapter_name, > short *adapter_nr, > - int mfe_shared) > + int mfe_shared, > + int (*fe_ioctl_override)(struct dvb_frontend *, > + unsigned int, void *, unsigned int)) > { > int result; > > @@ -159,6 +161,7 @@ > } > fe->adapter.priv = adapter_priv; > fe->adapter.mfe_shared = mfe_shared; > + fe->adapter.fe_ioctl_override = fe_ioctl_override; > > return result; > } > @@ -258,7 +261,9 @@ > void *adapter_priv, > struct device *device, > short *adapter_nr, > - int mfe_shared) > + int mfe_shared, > + int (*fe_ioctl_override)(struct dvb_frontend *, > + unsigned int, void *, unsigned int)) > { > struct list_head *list, *q; > struct videobuf_dvb_frontend *fe; > @@ -272,7 +277,7 @@ > > /* Bring up the adapter */ > res = videobuf_dvb_register_adapter(f, module, adapter_priv, device, > - fe->dvb.name, adapter_nr, mfe_shared); > + fe->dvb.name, adapter_nr, mfe_shared, fe_ioctl_override); > if (res < 0) { > printk(KERN_WARNING "videobuf_dvb_register_adapter failed > (errno = > %d)\n", res); > return res; > --- a/linux/include/media/videobuf-dvb.h Tue Jun 16 16:08:17 2009 -0400 > +++ b/linux/include/media/videobuf-dvb.h Sat May 23 17:00:59 2009 -0400 > @@ -42,7 +42,9 @@ > void *adapter_priv, > struct device *device, > short *adapter_nr, > - int mfe_shared); > + int mfe_shared, > + int (*fe_ioctl_override)(struct dvb_frontend *, > + unsigned int, void *, unsigned int)); > > void videobuf_dvb_unregister_bus(struct videobuf_dvb_frontends *f); > > --- a/linux/drivers/media/video/cx23885/cx23885-dvb.c Tue Jun 16 > 16:08:17 2009 -0400 > +++ b/linux/drivers/media/video/cx23885/cx23885-dvb.c Sat May 23 > 17:00:59 2009 -0400 > @@ -856,7 +856,7 @@ > > /* register everything */ > ret = videobuf_dvb_register_bus(&port->frontends, THIS_MODULE, port, > - &dev->pci->dev, adapter_nr, 0); > + &dev->pci->dev, adapter_nr, 0, NULL); > > /* init CI & MAC */ > switch (dev->board) { > --- a/linux/drivers/media/video/cx88/cx88-dvb.c Tue Jun 16 16:08:17 > 2009 -0400 > +++ b/linux/drivers/media/video/cx88/cx88-dvb.c Sat May 23 17:00:59 > 2009 -0400 > @@ -1180,7 +1180,7 @@ > > /* register everything */ > return videobuf_dvb_register_bus(&dev->frontends, THIS_MODULE, dev, > - &dev->pci->dev, adapter_nr, mfe_shared); > + &dev->pci->dev, adapter_nr, > mfe_shared, NULL); > > frontend_detach: > core->gate_ctrl = NULL; > --- a/linux/drivers/media/video/saa7134/saa7134-dvb.c Tue Jun 16 > 16:08:17 2009 -0400 > +++ b/linux/drivers/media/video/saa7134/saa7134-dvb.c Sat May 23 > 17:00:59 2009 -0400 > @@ -1509,7 +1509,7 @@ > > /* register everything else */ > ret = videobuf_dvb_register_bus(&dev->frontends, THIS_MODULE, dev, > - &dev->pci->dev, adapter_nr, 0); > + &dev->pci->dev, adapter_nr, 0, NULL); > > /* this sequence is necessary to make the tda1004x load its firmware > * and to enter analog mode of hybrid boards > > > > > Finally, the actual implementation of this new feature in the cx23885 > driver for the sake of RF input switching: > > --- a/linux/drivers/media/video/cx23885/cx23885-dvb.c Sat May 23 > 17:00:59 2009 -0400 > +++ b/linux/drivers/media/video/cx23885/cx23885-dvb.c Fri May 08 > 21:39:24 2009 -0400 > @@ -484,9 +484,33 @@ > } > break; > } > - return (port->set_frontend_save) ? > - port->set_frontend_save(fe, param) : -ENODEV; > + return 0; > } > + > +static int cx23885_dvb_fe_ioctl_override(struct dvb_frontend *fe, > + unsigned int cmd, void *parg, > + unsigned int stage) > +{ > + int err = 0; > + > + switch (stage) { > + case DVB_FE_IOCTL_PRE: > + > + switch (cmd) { > + case FE_SET_FRONTEND: > + err = cx23885_dvb_set_frontend(fe, > + (struct dvb_frontend_parameters *) parg); > + break; > + } > + break; > + > + case DVB_FE_IOCTL_POST: > + /* no post-ioctl handling required */ > + break; > + } > + return err; > +}; > + > > static int dvb_register(struct cx23885_tsport *port) > { > @@ -527,12 +551,6 @@ > 0x60, &dev->i2c_bus[1].i2c_adap, > &hauppauge_hvr127x_config); > } > - > - /* FIXME: temporary hack */ > - /* define bridge override to set_frontend */ > - port->set_frontend_save = fe0->dvb.frontend->ops.set_frontend; > - fe0->dvb.frontend->ops.set_frontend = cx23885_dvb_set_frontend; > - > break; > case CX23885_BOARD_HAUPPAUGE_HVR1255: > i2c_bus = &dev->i2c_bus[0]; > @@ -856,7 +874,8 @@ > > /* register everything */ > ret = videobuf_dvb_register_bus(&port->frontends, THIS_MODULE, port, > - &dev->pci->dev, adapter_nr, 0, NULL); > + &dev->pci->dev, adapter_nr, 0, > + cx23885_dvb_fe_ioctl_override); > > /* init CI & MAC */ > switch (dev->board) { > --- a/linux/drivers/media/video/cx23885/cx23885.h Sat May 23 17:00:59 > 2009 -0400 > +++ b/linux/drivers/media/video/cx23885/cx23885.h Fri May 08 21:39:24 > 2009 -0400 > @@ -289,10 +289,6 @@ > /* Allow a single tsport to have multiple frontends */ > u32 num_frontends; > void *port_priv; > - > - /* FIXME: temporary hack */ > - int (*set_frontend_save) (struct dvb_frontend *, > - struct dvb_frontend_parameters *); > }; > > struct cx23885_dev { > > > > > Again, the above changeset simply removes the old RF input path > switching hack, and implements the feature using the new frontend > ioctl override method instead. This is a much cleaner and more more > robust way to handle this, which actually opening doors for other > drivers to handle similar problems in a much more efficient manner. > > Please voice your comments about this particular change and any of its > implications in this thread. If all goes well, I'd like to merge this > into the master repository in time for the next merge window. Once > this is in the master branch, I can start working on removing other > similar hacks from other drivers in our tree, in favor of this better > method. > > Cheers, > > Michael Krufky > --
I'm all for it. Cheers, Hermann -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
