Re: [PATCH] dvb: Allow MAC addresses to be mapped to stable device names with udev

[Mauro Carvalho Chehab]

Em Wed, 31 Oct 2018 16:13:00 +0000
Sean Young <sean@xxxxxxxx> escreveu:

> On Wed, Oct 31, 2018 at 03:51:40PM +0000, David Howells wrote:
> > David Howells <dhowells@xxxxxxxxxx> wrote:
> >   
> > > > > > Devices without a mac address shouldn't have a mac_dvb sysfs attribute,
> > > > > > I think.  
> > > > > 
> > > > > I'm not sure that's possible within the core infrastructure.  It's a
> > > > > class attribute set when the class is created; I'm not sure it can be
> > > > > overridden on a per-device basis.
> > > > > 
> > > > > Possibly the file could return "" or "none" in this case?  
> > > > 
> > > > That's very ugly. Have a look at, for example, rc-core wakeup filters:
> > > > 
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/rc/rc-main.c#n1844  
> > > 
> > > By analogy, then, I think the thing to do is to put something like struct
> > > rc_dev::sysfs_groups[] into struct dvb_device (or maybe struct dvb_adapter)
> > > and then the dvb_mac attribute in there during dvb_register_device() based on
> > > whether or not the MAC address is not all zeros at that point.  
> > 
> > Hmmm...  This is trickier than it seems.  At the point the device struct is
> > registered, the MAC address hasn't yet been read:
> > 
> > [   13.865905] cx23885: CORE cx23885[1]: subsystem: 4254:0952, board: DVBSky S952 [card=50,autodetected]
> > [   14.095559] cx25840 8-0044: cx23885 A/V decoder found @ 0x88 (cx23885[1])
> > [   14.723127] cx25840 8-0044: loaded v4l-cx23885-avcore-01.fw firmware (16382 bytes)
> > [   14.738377] cx23885: cx23885_dvb_register() allocating 1 frontend(s)
> > [   14.738378] cx23885: cx23885[1]: cx23885 based dvb card
> > [   14.742536] i2c i2c-7: Added multiplexed i2c bus 9
> > [   15.096912] ts2020 9-0060: Montage Technology TS2022 successfully identified
> > [   15.096933] dvbdev: DVB: registering new adapter (cx23885[1])
> > [   15.096936] cx23885 0000:06:00.0: DVB: registering adapter 2 frontend 0 (Montage Technology M88DS3103)...
> > [   15.124665] cx23885: DVBSky S952 port 1 MAC address: 00:17:42:54:09:52
> > [   15.124666] cx23885: cx23885_dvb_register() allocating 1 frontend(s)
> > [   15.124674] cx23885: cx23885[1]: cx23885 based dvb card
> > [   15.128860] i2c i2c-6: Added multiplexed i2c bus 10
> > [   15.228172] ts2020 10-0060: Montage Technology TS2022 successfully identified
> > [   15.228188] dvbdev: DVB: registering new adapter (cx23885[1])
> > [   15.228190] cx23885 0000:06:00.0: DVB: registering adapter 3 frontend 0 (Montage Technology M88DS3103)...
> > [   15.255996] cx23885: DVBSky S952 port 2 MAC address: 00:17:42:54:09:53
> > [   15.255999] cx23885: cx23885_dev_checkrevision() Hardware revision = 0xa5
> > [   15.256004] cx23885: cx23885[1]/0: found at 0000:06:00.0, rev: 4, irq: 19, latency: 0, mmio: 0xf7a00000
> > 
> > The device structs are registered at 15.096936 and 15.228190 and this is the
> > point by which I think I have to set the device::groups pointer.
> > 
> > However, the device isn't fully initialised at this point and the MAC address
> > hasn't yet been read - and so the attribute doesn't appear.  proposed_mac is
> > set right after lines 15.124665 and 15.255996.  Interestingly, a third of a
> > second elapses between the device registration and the MAC being printed for
> > each adapter.  
> 
> device_create() will register the device in sysfs and send uevent. So, your
> original udev rule/code will not work, since it always would read
> a mac address of 0, as proposed_mac is not populated when the device is
> announced. That is, unless udev is scheduled after the mac is read.
> 
> I think the device_add/device_create() which triggers the uevent should be
> delayed until everything is available.

Yes. For udev rules to work, the very last thing to do is to create
devices.

In practice, dvb-usb/dvb-usb-v2 should delay calling 
dvb_register_device() until firmware is in warm state.

> 
> Sean
> 
> > 
> > Any suggestions?
> > 
> > David
> > ---
> > diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> > index b7171bf094fb..edbfa5549994 100644
> > --- a/drivers/media/dvb-core/dvbdev.c
> > +++ b/drivers/media/dvb-core/dvbdev.c
> > @@ -450,6 +450,23 @@ static int dvb_register_media_device(struct dvb_device *dvbdev,
> >  	return 0;
> >  }
> >  
> > +static ssize_t dvb_mac_show(struct device *dev,
> > +			    struct device_attribute *attr, char *buf)
> > +{
> > +	struct dvb_device *dvbdev = dev_get_drvdata(dev);
> > +
> > +	return sprintf(buf, "%pM\n", dvbdev->adapter->proposed_mac);
> > +}
> > +static DEVICE_ATTR_RO(dvb_mac);
> > +
> > +static struct attribute *dvb_device_attrs[] = {
> > +	&dev_attr_dvb_mac.attr,
> > +	NULL
> > +};
> > +static const struct attribute_group dvb_device_attr_grp = {
> > +	.attrs	= dvb_device_attrs,
> > +};
> > +
> >  int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
> >  			const struct dvb_device *template, void *priv,
> >  			enum dvb_device_type type, int demux_sink_pads)
> > @@ -533,6 +550,14 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
> >  
> >  	mutex_unlock(&dvbdev_register_lock);
> >  
> > +	if (adap->proposed_mac[0] || adap->proposed_mac[1] ||
> > +	    adap->proposed_mac[2] || adap->proposed_mac[3] ||
> > +	    adap->proposed_mac[4] || adap->proposed_mac[5]) {  
> 
> is_zero_ether_addr()
> 
> > +		dvbdev->sysfs_groups[0] = &dvb_device_attr_grp;
> > +		dvbdev->sysfs_groups[1] = NULL;
> > +		adap->device->groups = dvbdev->sysfs_groups;
> > +	}
> > +
> >  	clsdev = device_create(dvb_class, adap->device,
> >  			       MKDEV(DVB_MAJOR, minor),
> >  			       dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
> > @@ -1010,6 +1035,31 @@ void dvb_module_release(struct i2c_client *client)
> >  EXPORT_SYMBOL_GPL(dvb_module_release);
> >  #endif
> >  
> > +static ssize_t dvb_adapter_show(struct device *dev,
> > +				struct device_attribute *attr, char *buf)
> > +{
> > +	struct dvb_device *dvbdev = dev_get_drvdata(dev);
> > +
> > +	return sprintf(buf, "%d\n", dvbdev->adapter->num);
> > +}
> > +static DEVICE_ATTR_RO(dvb_adapter);
> > +
> > +static ssize_t dvb_type_show(struct device *dev,
> > +			     struct device_attribute *attr, char *buf)
> > +{
> > +	struct dvb_device *dvbdev = dev_get_drvdata(dev);
> > +
> > +	return sprintf(buf, "%s\n", dnames[dvbdev->type]);
> > +}
> > +static DEVICE_ATTR_RO(dvb_type);
> > +
> > +static struct attribute *dvb_class_attrs[] = {
> > +	&dev_attr_dvb_adapter.attr,
> > +	&dev_attr_dvb_type.attr,
> > +	NULL
> > +};
> > +ATTRIBUTE_GROUPS(dvb_class);
> > +
> >  static int dvb_uevent(struct device *dev, struct kobj_uevent_env *env)
> >  {
> >  	struct dvb_device *dvbdev = dev_get_drvdata(dev);
> > @@ -1050,6 +1100,7 @@ static int __init init_dvbdev(void)
> >  		retval = PTR_ERR(dvb_class);
> >  		goto error;
> >  	}
> > +	dvb_class->dev_groups = dvb_class_groups,
> >  	dvb_class->dev_uevent = dvb_uevent;
> >  	dvb_class->devnode = dvb_devnode;
> >  	return 0;
> > diff --git a/include/media/dvbdev.h b/include/media/dvbdev.h
> > index 881ca461b7bb..d6becdd2d56e 100644
> > --- a/include/media/dvbdev.h
> > +++ b/include/media/dvbdev.h
> > @@ -127,6 +127,7 @@ struct dvb_adapter {
> >   *
> >   * @list_head:	List head with all DVB devices
> >   * @fops:	pointer to struct file_operations
> > + * @sysfs_groups: Additional sysfs attributes
> >   * @adapter:	pointer to the adapter that holds this device node
> >   * @type:	type of the device, as defined by &enum dvb_device_type.
> >   * @minor:	devnode minor number. Major number is always DVB_MAJOR.
> > @@ -157,6 +158,7 @@ struct dvb_adapter {
> >  struct dvb_device {
> >  	struct list_head list_head;
> >  	const struct file_operations *fops;
> > +	const struct attribute_group *sysfs_groups[2];
> >  	struct dvb_adapter *adapter;
> >  	enum dvb_device_type type;
> >  	int minor;  



Thanks,
Mauro