linux-kernel - Re: [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and cmd

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Date:	Tue, 19 Jul 2016 18:22:53 +0200
From:	Richard Weinberger <richard@....at>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Andrey Smirnov <andrew.smirnov@...il.com>,
	linux-mtd@...ts.infradead.org,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and
 cmd_ctrl

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.

Thanks,
//richard