Hello,
Thank you for the review.
On 06/12/2013 03:05 PM, Grant Likely wrote:
On Tue, 11 Jun 2013 16:48:56 +0200, Florian Vaussard <florian.vaussard@xxxxxxx> wrote:
These constants can be used to easily declare MTD partitions inside
DTS.
The constants MTDPART_OFS_* are purposely not included. Indeed,
parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
Negative constants, as defined by MTDPART_OFS_*, would be wrongly
The DT binding uses the number of cells defined by #address-cells. It is
not fixed to a u32 or a u64
The message was ill-formatted, sorry. As an address cell is u32, and as
parse_ofpart_partitions() is storing the value inside u64 without checking
for sign extension (as one assumes to have only positive offsets),
passing a negative value would require 2 address cells, making it more
difficult
for the DT user. But as Stephen Warren noticed, it is probably desirable
to specify sizes >= 4GB, thus I will think about a way to easily handle
such case.
Anyway, MTDPART_OFS_* would probably face the same objection raised by
you for
MTDPART_SIZ_FULL.
interpreted by parse_ofpart_partitions(). Two cells should be
used to correctly encode the negative constants, but this breaks
current usage.
The binding doesn't even allow for shortcuts like MTDPART_SIZ_FULL. If a
partition fills the whole device, then the reg property should include
the actual size. If the code is allowing '0' to be used to mean
MTDPART_SIZ_FULL, then that is a bug that needs to be fixed.
The root problem is that many System on Module, like the Gumstix Overo, are
shipped with various NAND sizes depending on the version or even the
manufacturing
period. Supporting such a diversity would painfully duplicates lots of DT
code and clutter the arch/arm/boot/dts/ directory with dozens of slightly-
different versions. I believe that determining the NAND size is better done
at probe time, and this is what is currently done in legacy board files:
static struct mtd_partition overo_nand_partitions[] = {
{
.name = "xloader",
.offset = 0, /* Offset =
0x00000 */
.size = 4 * NAND_BLOCK_SIZE,
.mask_flags = MTD_WRITEABLE
},
<snip...>
{
.name = "rootfs",
.offset = MTDPART_OFS_APPEND, /* Offset =
0x680000 */
.size = MTDPART_SIZ_FULL,
},
};
Moreover, I do not see such strict restriction in the OF norm. If I
refer to IEEE
1275-1994 page 174, for the definition of the "reg" property, it is written:
"The interpretation of the size entries is dependent on the parent bus."
Nevertheless, if such an approach is not acceptable, could we think about an
alternative solution? Like a boolean property "mtd,append-and-fill" that
would
replace the "reg" property and tell the MTD core to compute the
partition size
at probe time, like what is currently done with board files?
Best regards,
Florian
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