On Tue, Jul 19, 2016 at 9:22 AM, Richard Weinberger <rich...@nod.at> wrote: > Am 19.07.2016 um 18:12 schrieb Boris Brezillon: >>>> Not sure a BUG_ON() is worst than a NULL-pointer exception ;-). >>> >>> When this really just triggers a NULL-pointer exception, we don't need a >>> BUG_ON or WARN_ON at >>> all since the kernel can tell anyway what went wrong. >> >> Hm, that's not entirely true, depending on your debug options you don't >> have all the information to guess which line triggered the NULL pointer >> exception, and this makes it harder to debug. >> And I agree with Andrey here, it's better to complain at registration >> time than letting the controller register all its NAND devices and >> generate exceptions when the NAND is really used. >> >> BTW, I don't quite understand the rational behind BUG_ON() eradication. >> I agree that they should not be used when the driver can recover from a >> specific failure, but that's not really the case here (some NAND >> controller drivers don't check nand_scan_tail() or nand_scan() return >> code). > > I've been told that new code (except core code) should not BUG()/_ON(). > >> The best solution would probably be to patch all those drivers and then >> return an error when one of the mandatory hooks is missing, but in the >> meantime I don't see any problem in adding BUG_ON() calls. > > Yes, definitely.
I don't have any preferences as far BUG_ON/WARN_ON are concerned and am more than happy to change one for another. The reason I came up with that patch is that I stumbled on that segfault (by not providing custom select_chip() and not setting up cmd_ctrl()) and it took me good 20 minutes to figure out the nature of the problem, whereas, IMHO, having a BUG/WARN statement at the would have been more self-documenting/explanatory. What if I modify the patch to change nand_set_default's signature to return a error code, add corresponding checking in nand_get_flash_type()/nand_scan_ident() and replace BUG_ON with WARN_ON? Would it be more agreeable solution? Andrey