mtd: part: Create the master device node when partitioned
For many use cases, it helps to have a device node for the entire MTD device as well as device nodes for the individual partitions. For example, this allows querying the entire device's properties. A common idiom is to create an additional partition which spans over the whole device. This patch makes a config option, CONFIG_MTD_PARTITIONED_MASTER, which makes the master partition present even when the device is partitioned. This isn't turned on by default since it presents a backwards-incompatible device numbering. The patch also makes the parent of a partition device be the master, if the config flag is set, now that the master is a full device. Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org> Signed-off-by: Brian Norris <computersforpeace@gmail.com>
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@ -309,6 +309,19 @@ config MTD_SWAP
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The driver provides wear leveling by storing erase counter into the
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OOB.
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config MTD_PARTITIONED_MASTER
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bool "Retain master device when partitioned"
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default n
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depends on MTD
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help
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For historical reasons, by default, either a master is present or
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several partitions are present, but not both. The concern was that
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data listed in multiple partitions was dangerous; however, SCSI does
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this and it is frequently useful for applications. This config option
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leaves the master in even if the device is partitioned. It also makes
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the parent of the partition device be the master device, rather than
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what lies behind the master.
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source "drivers/mtd/chips/Kconfig"
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source "drivers/mtd/maps/Kconfig"
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@ -38,6 +38,7 @@
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#include <linux/gfp.h>
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#include <linux/slab.h>
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#include <linux/reboot.h>
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#include <linux/kconfig.h>
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#include <linux/mtd/mtd.h>
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#include <linux/mtd/partitions.h>
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@ -501,6 +502,29 @@ out_error:
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return ret;
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}
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static int mtd_add_device_partitions(struct mtd_info *mtd,
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struct mtd_partition *real_parts,
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int nbparts)
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{
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int ret;
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if (nbparts == 0 || IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) {
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ret = add_mtd_device(mtd);
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if (ret == 1)
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return -ENODEV;
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}
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if (nbparts > 0) {
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ret = add_mtd_partitions(mtd, real_parts, nbparts);
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if (ret && IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
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del_mtd_device(mtd);
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return ret;
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}
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return 0;
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}
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/**
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* mtd_device_parse_register - parse partitions and register an MTD device.
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*
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@ -523,7 +547,8 @@ out_error:
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* found this functions tries to fallback to information specified in
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* @parts/@nr_parts.
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* * If any partitioning info was found, this function registers the found
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* partitions.
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* partitions. If the MTD_PARTITIONED_MASTER option is set, then the device
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* as a whole is registered first.
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* * If no partitions were found this function just registers the MTD device
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* @mtd and exits.
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*
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@ -534,27 +559,21 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
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const struct mtd_partition *parts,
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int nr_parts)
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{
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int err;
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struct mtd_partition *real_parts;
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int ret;
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struct mtd_partition *real_parts = NULL;
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err = parse_mtd_partitions(mtd, types, &real_parts, parser_data);
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if (err <= 0 && nr_parts && parts) {
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ret = parse_mtd_partitions(mtd, types, &real_parts, parser_data);
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if (ret <= 0 && nr_parts && parts) {
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real_parts = kmemdup(parts, sizeof(*parts) * nr_parts,
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GFP_KERNEL);
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if (!real_parts)
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err = -ENOMEM;
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ret = -ENOMEM;
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else
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err = nr_parts;
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ret = nr_parts;
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}
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if (err > 0) {
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err = add_mtd_partitions(mtd, real_parts, err);
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kfree(real_parts);
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} else if (err == 0) {
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err = add_mtd_device(mtd);
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if (err == 1)
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err = -ENODEV;
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}
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if (ret >= 0)
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ret = mtd_add_device_partitions(mtd, real_parts, ret);
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/*
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* FIXME: some drivers unfortunately call this function more than once.
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@ -569,7 +588,8 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
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register_reboot_notifier(&mtd->reboot_notifier);
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}
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return err;
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kfree(real_parts);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mtd_device_parse_register);
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@ -30,6 +30,7 @@
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#include <linux/mtd/mtd.h>
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#include <linux/mtd/partitions.h>
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#include <linux/err.h>
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#include <linux/kconfig.h>
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#include "mtdcore.h"
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@ -379,10 +380,17 @@ static struct mtd_part *allocate_partition(struct mtd_info *master,
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slave->mtd.name = name;
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slave->mtd.owner = master->owner;
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/* NOTE: we don't arrange MTDs as a tree; it'd be error-prone
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* to have the same data be in two different partitions.
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/* NOTE: Historically, we didn't arrange MTDs as a tree out of
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* concern for showing the same data in multiple partitions.
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* However, it is very useful to have the master node present,
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* so the MTD_PARTITIONED_MASTER option allows that. The master
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* will have device nodes etc only if this is set, so make the
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* parent conditional on that option. Note, this is a way to
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* distinguish between the master and the partition in sysfs.
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*/
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slave->mtd.dev.parent = master->dev.parent;
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slave->mtd.dev.parent = IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) ?
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&master->dev :
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master->dev.parent;
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slave->mtd._read = part_read;
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slave->mtd._write = part_write;
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@ -631,8 +639,8 @@ EXPORT_SYMBOL_GPL(mtd_del_partition);
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* and registers slave MTD objects which are bound to the master according to
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* the partition definitions.
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*
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* We don't register the master, or expect the caller to have done so,
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* for reasons of data integrity.
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* For historical reasons, this function's caller only registers the master
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* if the MTD_PARTITIONED_MASTER config option is set.
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*/
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int add_mtd_partitions(struct mtd_info *master,
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