On 18 September 2014 04:00, Brian Norris <computersforpeace@xxxxxxxxx> wrote:
> On Mon, Sep 15, 2014 at 11:27:43AM +0300, Roger Quadros wrote:
>> On 09/12/2014 07:56 PM, Ezequiel Garcia wrote:
>> > On 12 Sep 12:01 PM, Roger Quadros wrote:
>> >> On 09/11/2014 04:47 PM, Ezequiel Garcia wrote:
>> >>> This commit adds a hidden option to build the omap_elm as a module, if
>> >>> omap2_nand is a module (and similarly in the built-in case).
>> >>>
>> >>> This fixes the following build error when omap2_nand is chosen built-in,
>> >>> and omap_elm is chosen as a module:
>> >>>
>> >>> drivers/built-in.o: In function `omap_nand_probe':
>> >>> /work/linux-2.6/drivers/mtd/nand/omap2.c:2010: undefined reference to `elm_config'
>> >>> /work/linux-2.6/drivers/mtd/nand/omap2.c:1980: undefined reference to `elm_config'
>> >>> /work/linux-2.6/drivers/mtd/nand/omap2.c:1927: undefined reference to `elm_config'
>> >>> drivers/built-in.o: In function `omap_elm_correct_data':
>> >>> /work/linux-2.6/drivers/mtd/nand/omap2.c:1444: undefined reference to `elm_decode_bch_error_page'
>> >>>
>> >>> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>
>> >>> ---
>> >>> drivers/mtd/nand/Kconfig | 8 +++++++-
>> >>> drivers/mtd/nand/Makefile | 2 +-
>> >>> 2 files changed, 8 insertions(+), 2 deletions(-)
>> >>>
>> >>> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
>> >>> index f1cf503..12e8ee8 100644
>> >>> --- a/drivers/mtd/nand/Kconfig
>> >>> +++ b/drivers/mtd/nand/Kconfig
>> >>> @@ -96,7 +96,7 @@ config MTD_NAND_OMAP2
>> >>>
>> >>> config MTD_NAND_OMAP_BCH
>> >>> depends on MTD_NAND_OMAP2
>> >>> - tristate "Support hardware based BCH error correction"
>> >>> + bool "Support hardware based BCH error correction"
>> >>> default n
>> >>> select BCH
>> >>> help
>> >>> @@ -106,6 +106,12 @@ config MTD_NAND_OMAP_BCH
>> >>> legacy OMAP families like OMAP2xxx, OMAP3xxx do not have ELM engine
>> >>> so they should not enable this config symbol.
>> >>>
>> >>> +config MTD_NAND_OMAP_BCH_BUILD
>> >>> + tristate
>> >>> + depends on MTD_NAND_OMAP2
>> >>> + default m if MTD_NAND_OMAP2=m && MTD_NAND_OMAP_BCH
>> >>> + default y if MTD_NAND_OMAP2=y && MTD_NAND_OMAP_BCH
>
> I think the last 2 lines could be combined:
>
> default MTD_NAND_OMAP2 if MTD_NAND_OMAP_BCH
>
>> >>> +
>> >>> config MTD_NAND_IDS
>> >>> tristate
>> >>>
>> >>> diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
>> >>> index 4bcdeb0..3580188 100644
>> >>> --- a/drivers/mtd/nand/Makefile
>> >>> +++ b/drivers/mtd/nand/Makefile
>> >>> @@ -27,7 +27,7 @@ obj-$(CONFIG_MTD_NAND_NDFC) += ndfc.o
>> >>> obj-$(CONFIG_MTD_NAND_ATMEL) += atmel_nand.o
>> >>> obj-$(CONFIG_MTD_NAND_GPIO) += gpio.o
>> >>> obj-$(CONFIG_MTD_NAND_OMAP2) += omap2_nand.o
>> >>> -obj-$(CONFIG_MTD_NAND_OMAP_BCH) += omap_elm.o
>> >>> +obj-$(CONFIG_MTD_NAND_OMAP_BCH_BUILD) += omap_elm.o
>> >>> obj-$(CONFIG_MTD_NAND_CM_X270) += cmx270_nand.o
>> >>> obj-$(CONFIG_MTD_NAND_PXA3xx) += pxa3xx_nand.o
>> >>> obj-$(CONFIG_MTD_NAND_TMIO) += tmio_nand.o
>
> Apparently I came up with a nearly identical solution, so it must be
> good! ;)
>
>> >> The overall logic seems to work but I still see the following issue.
>> >>
>> >> In menuconfig, the OMAP_BCH option is still visible as a boolean even though
>> >> the ELM module finally gets built as a module.
>> >> This can be confusing to the user and I'd avoid that behaviour.
>> >>
>> >
>> > Yes, I know. But it's either this solution or no solution at all, I think.
>> >
>> > Let me give some further context about this patch, so we can have more
>> > information to decide.
>> >
>> > First of all (and IMO) the user doesn't have to know about the ELM being
>> > a module or not, because modprobe will load it (since omap2_nand depends
>> > on omap_elm's symbols).
>> >
>> > So, the new way seems a bit more intuitive for me. The user choses if he
>> > wants to have hardware BCH support, and such support gets built the right
>> > way.
>> >
>> > If we still consider this highly confusing, and we want to avoid it,
>> > then it seems we can only make omap_elm a boolean, which means it'll always
>> > be built-in. I crafted this patch in an effort to avoid making it boolean.
>> >
>> > Finally, the solution is taken from media/usb/stk1160. For good or for bad,
>> > we have a precedent in doing things this way.
>> >
>> > Ultimately, I don't care much as I don't think anyone will build it as a module,
>> > except maybe for testing the driver under probe/remove cycles.
>> >
>> OK. I personally prefer boolean than the Kconfig magic as it makes my life a bit
>> easier and less confusing to the user i.e. wysiwyg ;).
>>
>> Let's see what the MTD maintainers prefer.
>> Brian and David, any insights on this problem?
>
> It seems like 'elm' serves more as an accessory piece of omap2.{o,ko},
> not really a separate module, so it's possible it'd make your life even
> easier to just link elm.o into omap2.o. There's no requirement that two
> source files create two separate kernel modules. I think this would
> present the simplest possible interface to the user.
>
> Thoughts?
>
Yeah, but that means a larger refactoring, because now you'd have to
call the ELM driver probe() from the NAND driver probe().
It'd be a nice cleanup, but maybe this is the second step?
--
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar
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