Re[4]: [PATCH 06/12] mtd: nand: remove a bunch of unused commands

[Alexander Shiyan]

> 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

OK, for Samsung chips too.

> 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

Where it breaks? "rtc_from4_hwcontrol" use writeb() for "cmd" parameter,
so its not breaks. Is I think incorrect?

> rtc_from4.c. Unforunately, no one bothered to actually document this
> within nand_command_lp, but such is life.

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