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Message-ID: <20151112001550.GD96199@google.com>
Date: Wed, 11 Nov 2015 16:15:50 -0800
From: Brian Norris <computersforpeace@...il.com>
To: Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc: David Woodhouse <dwmw2@...radead.org>,
linux-mtd@...ts.infradead.org,
Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
Marek Vasut <marex@...x.de>,
Scott Wood <scottwood@...escale.com>,
Josh Wu <josh.wu@...el.com>,
Robert Jarzmik <robert.jarzmik@...e.fr>,
Kyungmin Park <kyungmin.park@...sung.com>,
Han Xu <han.xu@...escale.com>, Stefan Agner <stefan@...er.ch>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 13/11] mtd: assign mtd->dev.of_node when creating
partition devices
On Mon, Nov 02, 2015 at 01:38:41AM +0100, Boris Brezillon wrote:
> MTD partitions may have been created from a DT definition, and in this case
> the ->of_node of the struct device embedded in mtd_info should point to
> the DT node that was used to create the partition.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
I like the idea of this patch, but I'm not sure about all of its
details.
> ---
> Hi Brian,
>
> Yet another patch that IMO should go into your "mtd: migrate 'of_node'
> handling to core, not in mtd_part_parser_data" series.
>
> Best Regards,
>
> Boris
>
> drivers/mtd/mtdcore.c | 17 +++++++++++++----
> drivers/mtd/mtdpart.c | 3 +++
> drivers/mtd/ofpart.c | 1 +
> include/linux/mtd/partitions.h | 1 +
> 4 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index b1eea48..6101288 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -32,6 +32,7 @@
> #include <linux/err.h>
> #include <linux/ioctl.h>
> #include <linux/init.h>
> +#include <linux/of.h>
> #include <linux/proc_fs.h>
> #include <linux/idr.h>
> #include <linux/backing-dev.h>
> @@ -584,11 +585,13 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
> const struct mtd_partition *parts,
> int nr_parts)
> {
> - int ret;
> + int ret, i;
> struct mtd_partition *real_parts = NULL;
>
> ret = parse_mtd_partitions(mtd, types, &real_parts, parser_data);
> - if (ret <= 0 && nr_parts && parts) {
> + if (ret > 0) {
> + nr_parts = ret;
> + } else if (nr_parts && parts) {
> real_parts = kmemdup(parts, sizeof(*parts) * nr_parts,
> GFP_KERNEL);
> if (!real_parts)
> @@ -604,7 +607,7 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
> ret = 0;
> }
>
> - ret = mtd_add_device_partitions(mtd, real_parts, ret);
> + ret = mtd_add_device_partitions(mtd, real_parts, nr_parts);
> if (ret)
> goto out;
>
> @@ -623,7 +626,13 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
> }
>
> out:
> - kfree(real_parts);
> + if (real_parts) {
> + for (i = 0; i < nr_parts; i++)
> + of_node_put(real_parts[i].of_node);
> +
> + kfree(real_parts);
> + }
> +
> return ret;
> }
> EXPORT_SYMBOL_GPL(mtd_device_parse_register);
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index f8ba153..95f3a0d 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -29,6 +29,7 @@
> #include <linux/kmod.h>
> #include <linux/mtd/mtd.h>
> #include <linux/mtd/partitions.h>
> +#include <linux/of.h>
> #include <linux/err.h>
> #include <linux/kconfig.h>
>
> @@ -319,6 +320,7 @@ static int part_block_markbad(struct mtd_info *mtd, loff_t ofs)
>
> static inline void free_partition(struct mtd_part *p)
> {
> + of_node_put(mtd_get_of_node(&p->mtd));
> kfree(p->mtd.name);
> kfree(p);
> }
> @@ -391,6 +393,7 @@ static struct mtd_part *allocate_partition(struct mtd_info *master,
> slave->mtd.dev.parent = IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) ?
> &master->dev :
> master->dev.parent;
> + mtd_set_of_node(&slave->mtd, of_node_get(part->of_node));
>
> slave->mtd._read = part_read;
> slave->mtd._write = part_write;
> diff --git a/drivers/mtd/ofpart.c b/drivers/mtd/ofpart.c
> index f78d2ae..5c64e04 100644
> --- a/drivers/mtd/ofpart.c
> +++ b/drivers/mtd/ofpart.c
> @@ -111,6 +111,7 @@ static int parse_ofpart_partitions(struct mtd_info *master,
> if (of_get_property(pp, "lock", &len))
> (*pparts)[i].mask_flags |= MTD_POWERUP_LOCK;
>
> + (*pparts)[i].of_node = of_node_get(pp);
I don't think we should mix up too much of the error handling between
ofpart.c and mtdcore.c (right now, you do of_node_get() here but the
of_node_put() is forced into mtdcore.c). I think the problem here is the
same as the problem with Linus' patch here:
http://lists.infradead.org/pipermail/linux-mtd/2015-November/063219.html
It's just too easy to leak resources when MTD parsers don't have their
own cleanup functions (like C++ destructors, or the driver model's
remove() function, or so many other resource models). If we had a
cleanup function, then we could just put the release handling there.
But actually, I don't think we need to 'get' the property here; we only
need to 'get' it when we're putting it somewhere that will actually use
it long term. i.e., when it actually gets assigned to the
mtd.dev.of_node field and is headed for sysfs.
IOW, I think we can grab the reference in add_mtd_device() and drop it
in del_mtd_device(). This would handle both the partition and
non-partition case the same.
I have a patch to do that (for the non-partition case) queued up. I'll
push it out soon, then I expect you can make this patch a lot simpler.
Brian
> i++;
> }
>
> diff --git a/include/linux/mtd/partitions.h b/include/linux/mtd/partitions.h
> index 773975a..282644c 100644
> --- a/include/linux/mtd/partitions.h
> +++ b/include/linux/mtd/partitions.h
> @@ -42,6 +42,7 @@ struct mtd_partition {
> uint64_t offset; /* offset within the master MTD space */
> uint32_t mask_flags; /* master MTD flags to mask out for this partition */
> struct nand_ecclayout *ecclayout; /* out of band layout for this partition (NAND only) */
> + struct device_node *of_node; /* OF node attached to the partition */
> };
>
> #define MTDPART_OFS_RETAIN (-3)
> --
> 2.1.4
>
--
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