On Thu, 31 Mar 2022 11:45:47 +0200, Takashi Iwai wrote: > > On Thu, 31 Mar 2022 11:34:38 +0200, > Heikki Krogerus wrote: > > > > On Thu, Mar 31, 2022 at 11:28:20AM +0200, Takashi Iwai wrote: > > > On Thu, 31 Mar 2022 11:25:43 +0200, > > > Heikki Krogerus wrote: > > > > > > > > On Thu, Mar 31, 2022 at 11:12:55AM +0200, Takashi Iwai wrote: > > > > > > > > - if (!strcmp(dev->driver->name, "i915") && > > > > > > > > + if (dev->driver && !strcmp(dev->driver->name, "i915") && > > > > > > > > > > > > > > Can NULL dev->driver be really seen? I thought the components are > > > > > > > added by the drivers, hence they ought to have the driver field set. > > > > > > > But there can be corner cases I overlooked. > > > > > > > > > > > > > > > > > > > > > thanks, > > > > > > > > > > > > > > Takashi > > > > > > > > > > > > Hi Takashi, > > > > > > > > > > > > When I try using component_add in a different driver (usb4 in my > > > > > > case), I think dev->driver here is NULL because the i915 drivers do > > > > > > not have their component master fully bound when this new component is > > > > > > registered. When I test it, it seems to be causing a crash. > > > > > > > > > > Hm, from where component_add*() is called? Basically dev->driver must > > > > > be already set before the corresponding driver gets bound at > > > > > __driver_probe_deviec(). So, if the device is added to component from > > > > > the corresponding driver's probe, dev->driver must be non-NULL. > > > > > > > > The code that declares a device as component does not have to be the > > > > driver of that device. > > > > > > > > In our case the components are USB ports, and they are devices that > > > > are actually never bind to any drivers: drivers/usb/core/port.c > > > > > > OK, that's what I wanted to know. It'd be helpful if it's more > > > clearly mentioned in the commit log. > > > > Agree. > > > > > BTW, the same problem must be seen in MEI drivers, too. > > > > Wasn't there a patch for those too? I lost track... > > I don't know, I just checked the latest Linus tree. > > And, looking at the HD-audio code, I still wonder how NULL dev->driver > can reach there. Is there any PCI device that is added to component > without binding to a driver? We have dev_is_pci() check at the > beginning, so non-PCI devices should bail out there... Further reading on, I'm really confused. How data=NULL can be passed to this function? The data argument is the value passed from the component_match_add_typed() call in HD-audio driver, hence it must be always the snd_hdac_bus object. And, I guess the i915 string check can be omitted completely, at least, for HD-audio driver. It already have a check of the parent of the device and that should be enough. Takashi
