From: David Brownell on

--- On Wed, 8/4/10, David Woodhouse <dwmw2(a)> wrote:

> > Point is to ensure that enough of the right context
> > information is available to initialize correctly.
> > So the right data is extracted and passed on.

And also, ISTR, that the mechanism is general
enough to work with both MTD and EEPROM ...

> Forgive me if I'm being dim (and in particular, please
> forgive me if I'm
> going over something that was already discussed; I know
> it's been a
> while).

I also am at risk of getting lost in a pile
of hypotheticals which have been left behind
earlier in these threads.

But I don't see why it needs to be passed through
> the core MTD code.
> To take the simple case of an unpartitioned MTD device --
> why can't the
> map driver (or whatever) just call the maccessor setup
> function for
> itself, directly, right after calling add_mtd_device() with
> its newly-probed MTD device?

No idea, except that doing it once rather than
modifying every driver would seem healthier.
Surely changing all drivers is a Bad Thing.

> And for partitions, why can't it do the same, on the
> appropriate partition.
> OK, the answer to the latter question is that you don't
> actually *have*
> the pointers to each partition you register. But that's
> easily fixed.
> If we make add_mtd_partitions() take an extra 'struct
> mtd_info **'
> argument and put pointers to the slave mtd 'devices' into
> that, it means
> that your board driver *can* reliably get the mtd pointer
> for the fourth
> partition, or whatever it needs. And can then just do the
> memory
> accessor setup for itself.
> Isn't that enough?

Might be. Not my patch though... You asked why
the context was needed along with the partition
data (otherwise not available); I answered.

Still haven't seen a better patch though.

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From: David Woodhouse on
On Fri, 2010-08-06 at 12:18 +0530, Sudhakar Rajashekhara wrote:
> Thanks for the feedback. I'll be re-working on this patch and will
> re-post
> the updated patch soon.

Start with this, perhaps...

Subject: mtd/partitions: Add add_mtd_partitions_ret() function

Some callers want access to the MTD devices which get registered for
them when they call add_mtd_partitions(). Add a variant on the function
which does that.

Signed-off-by: David Woodhouse <David.Woodhouse(a)>

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index 4c539de..b9ee79b 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -522,26 +522,36 @@ out_register:
* for reasons of data integrity.

-int add_mtd_partitions(struct mtd_info *master,
- const struct mtd_partition *parts,
- int nbparts)
+int add_mtd_partitions_ret(struct mtd_info *master,
+ const struct mtd_partition *parts,
+ int nbparts, struct mtd_info ***mtds_ret)
struct mtd_part *slave;
uint64_t cur_offset = 0;
+ struct mtd_info **mtds = NULL;
int i;

printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);

+ if (mtds_ret) {
+ mtds = kmalloc(sizeof(*mtds) * nbparts, GFP_KERNEL);
+ if (!mtds)
+ return -ENOMEM;
+ }
for (i = 0; i < nbparts; i++) {
slave = add_one_partition(master, parts + i, i, cur_offset);
- if (!slave)
+ if (!slave) {
+ kfree(mtds);
return -ENOMEM;
+ }
cur_offset = slave->offset + slave->mtd.size;

+ if (mtds_ret)
+ *mtds_ret = mtds;
return 0;

static DEFINE_SPINLOCK(part_parser_lock);
static LIST_HEAD(part_parsers);
diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
index 274b619..f7935fa 100644
--- a/include/linux/mtd/partitions.h
+++ b/include/linux/mtd/partitions.h
@@ -49,9 +49,12 @@ struct mtd_partition {

struct mtd_info;

-int add_mtd_partitions(struct mtd_info *, const struct mtd_partition *, int);
+int add_mtd_partitions_ret(struct mtd_info *, const struct mtd_partition *, int,
+ struct mtd_info ***);
int del_mtd_partitions(struct mtd_info *);

+#define add_mtd_partitions(m, p, n) add_mtd_partitions_ret(m, p, n, NULL)
* Functions dealing with the various ways of partitioning the space

David Woodhouse Open Source Technology Centre
David.Woodhouse(a) Intel Corporation

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