Le Thu, 1 Jun 2017 11:43:40 -0700, Brian Norris <[email protected]> a écrit :
> 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 <[email protected]> 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 <[email protected]> > > > --- > > > 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? Well, I think it's already broken. AFAICT this driver does not implement ->_erase(), and mtd_erase() does not check if MTD_NO_ERASE is set before calling mtd->_erase(), neither UBI does before calling mtd_erase(). Between a NULL pointer exception and a div-by-zero exception, I can't decide what is better :-). IMO, we'd better add a check in UBI to refuse to attach a device with MTD_NO_ERASE or mtd->erasesize == 0, and fix other places that don't check erasesize value instead of putting a fake erasesize and using a dummy ->_erase() implementation for those devices that simply can't be erased. We should also probably complain with -ENOTSUPP when someone calls mtd_erase() on a device with MTD_NO_ERASE and add more checks in the add_mtd_device() to detect drivers that don't have MTD_NO_ERASE set and do not implement ->_erase() or leave ->erasesize to 0. > > 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. Fair enough.
