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    SubjectRe: [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and cmd_ctrl
    On Tue, 19 Jul 2016 11:11:54 -0700
    Andrey Smirnov <andrew.smirnov@gmail.com> wrote:

    > On Tue, Jul 19, 2016 at 9:22 AM, Richard Weinberger <richard@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?

    Agreed.


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