Re: [PATCH 3/4] mtd: mchp23k256: add partitioning support

Brian Norris
2017-06-01T18:43:45Z

On Wed, May 17, 2017 at 05:29:11PM +0200, Boris Brezillon wrote:
> Hi Chris,
>
> On Wed, 17 May 2017 17:39:07 +1200
> Chris Packham <chris.packham@alliedtelesis.co.nz> wrote:
>
> > Setting the of_node for the mtd device allows the generic mtd code to
> > setup the partitions. Additionally we must specify a non-zero erasesize
> > for the partitions to be writeable.
> >
> > Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> > ---
> > drivers/mtd/devices/mchp23k256.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/mtd/devices/mchp23k256.c b/drivers/mtd/devices/mchp23k256.c
> > index 2542f5b8b63f..02c6b9dcbd3e 100644
> > --- a/drivers/mtd/devices/mchp23k256.c
> > +++ b/drivers/mtd/devices/mchp23k256.c
> > @@ -143,6 +143,7 @@ static int mchp23k256_probe(struct spi_device *spi)
> >
> > data = dev_get_platdata(&spi->dev);
> >
> > + mtd_set_of_node(&flash->mtd, spi->dev.of_node);
> > flash->mtd.dev.parent = &spi->dev;
> > flash->mtd.type = MTD_RAM;
> > flash->mtd.flags = MTD_CAP_RAM;
> > @@ -151,6 +152,10 @@ static int mchp23k256_probe(struct spi_device *spi)
> > flash->mtd._read = mchp23k256_read;
> > flash->mtd._write = mchp23k256_write;
> >
> > + flash->mtd.erasesize = PAGE_SIZE;
> > + while (flash->mtd.size & (flash->mtd.erasesize - 1))
> > + flash->mtd.erasesize >>= 1;
> > +
>
> Can we fix allocate_partition() to properly handle the
> master->erasesize == 0 case instead of doing that?

Is everything actually ready for the eraseblock size to be 0? That would
seem surprising to many applications, I would think. Can you, for
instance, even use UBI on such a device?

BTW, I feel like this check is a little more natural to do with
'mtd->flags & MTD_NO_ERASE', rather than checking the (apparently
meaningless) erasesize.

(I realize there's a later version of these patches, but I figured I'd
put my comments where the suggestion was brought up.)

Brian