On Tue, Apr 28, 2015 at 4:53 AM, Brian Norris <computersforpe...@gmail.com> wrote: > On Tue, Apr 28, 2015 at 12:19:16AM +0200, Richard Weinberger wrote: >> Am 27.04.2015 um 23:35 schrieb Ben Shelton: >> > I tested this against the latest version of the PL353 NAND driver that >> > Punnaiah >> > has been working to upstream (copying her on this message). With a few >> > changes >> > to that driver, I got it most of the way through initialization with >> > on-die ECC >> > enabled, but it segfaults here with a null pointer dereference because the >> > PL353 driver does not implement chip->cmd_ctrl. Instead, it implements a >> > custom override of cmd->cmdfunc that does not call cmd_ctrl. Looking >> > through >> > the other in-tree NAND drivers, it looks like most of them do implement >> > cmd_ctrl, but quite a few of them do not (e.g. au1550nd, denali, docg4). >> > >> > What do you think would be the best way to handle this? It seems like >> > this gap >> > could be bridged from either side -- either the PL353 driver could >> > implement >> > cmd_ctrl, at least as a stub version that provides the expected behavior in >> > this case; or the on-die framework could break this out into a callback >> > function with a default implementation that the driver could override to >> > perform this behavior in the manner of its choosing. >> >> Oh, I thought every driver has to implement that function. ;-\ > > Nope. > >> But you're right there is a corner case. > > And it's not the only one! Right now, there's no guarantee even that > read_buf() returns raw data, unmodified by the SoC's controller. Plenty > of drivers actually have HW-enabled ECC turned on by default, and so > they override the chip->ecc.read_page() (and sometimes > chip->ecc.read_page_raw() functions, if we're lucky) with something > that pokes the appropriate hardware instead. I expect anything > comprehensive here is probably going to have to utilize > chip->ecc.read_page_raw(), at least if it's provided by the hardware > driver.
Yes, overriding the chip->ecc.read_page_raw would solve this. Agree that read_buf need not be returning raw data always including my new driver for arasan nand flash controller. http://lkml.iu.edu/hypermail/linux/kernel/1504.2/00313.html Regards, Punnaiah > >> What we could do is just using chip->cmdfunc() with a custom NAND command. >> i.e. chip->cmdfunc(mtd, NAND_CMD_READMODE, -1, -1); >> >> Gerhard Sittig tried to introduce such a command some time ago: >> http://lists.infradead.org/pipermail/linux-mtd/2014-April/053115.html > > Yikes! Please no! It's bad enough to have a ton of drivers doing > switch/case on a bunch of real, somewhat well-known opcodes, but to add > new fake ones? I'd rather not. We're inflicting ourselves with a > kernel-internal version of ioctl(). What's the justification, again? I > don't really remember the context of Gerhard's previous patch. > > Brian > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/