[PATCH 06/12] mtd: nand: remove a bunch of unused commands

[Brian Norris]

On Mon, Mar 4, 2013 at 11:29 AM, Alexander Shiyan <shc_work at mail.ru> wrote:
>> On Mon, Mar 4, 2013 at 8:42 AM, Artem Bityutskiy <dedekind1 at gmail.com> wrote:
>> > From: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
>> >
>> > Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
>> > ---
>> >  drivers/mtd/nand/cafe_nand.c   |    6 ------
>> >  drivers/mtd/nand/nand_base.c   |   10 ----------
>> >  drivers/mtd/nand/nandsim.c     |    8 --------
>> >  drivers/mtd/nand/nuc900_nand.c |    9 ---------
>> >  include/linux/mtd/nand.h       |   20 --------------------
>> >  5 files changed, 53 deletions(-)
>> >
>>
>> ... trimmed ...
> ...
>> > - * Note: the command for NAND_CMD_DEPLETE1 is really 0x00 but
>> > - *       there is no way to distinguish that from NAND_CMD_READ0
>> > - *       until the remaining sequence of commands has been completed
>> > - *       so add a high order bit and mask it off in the command.
>> > - */
>> > -#define NAND_CMD_DEPLETE1      0x100
>>
>> Perhaps this is the reason for the "unnecessary command masking" noted
>> by Alexander? There is one instance of a command function which masks
>> command & 0xff. Maybe Alexander's patch can be updated to mention this
>> likely cause for the original masking and can be applied on top of
>> Artem's cleanup series? Anyway, the mask was likely not used anyway,
>> since (as Artem mentions in this patch series) AG-AND had very little
>> general use (or none?).
>
> My patch is cleanup only. I think that the mask was originally included to
> limit the byte boundaries. However, this is not necessary because callback
> functions "cmd_ctrl" use writeb/iowrite8 for send command, ie do not allow
> the use of the wrong size. Address also passed to "cmd_ctrl" via "cmd"
> parameter, which is not masked but only shifted, i.e. we have a values
> above 0xff, so that is not a problem.

To be clear, I'm referring to your patch:

  [PATCH 1/3] mtd: nand_base: Removed unnecessary command masking

The function that you are editing (nand_command_lp) can be used for
AG-AND devices. The driver (rtc_from4.c - slated for removal in this
series) can send NAND_CMD_DEPLETE1, which according to the comments in
nand.h that I highlight above, should be "mask[ed] ... off in the
command". So without Artem's change, your patch is actually breaking
rtc_from4.c. Unforunately, no one bothered to actually document this
within nand_command_lp, but such is life.

Brian