Hi Richard,
Hm, the subject is not accurate. Should be something like that instead:
mtd: Avoid probe failures when mtd->dbg.dfs_dir is invalid
I can resend a version fixing that if you want.
Regards,
Boris
On Sat, 11 Nov 2017 15:46:14 +0100
Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> wrote:
> Commit e8e3edb95ce6 ("mtd: create per-device and module-scope debugfs
> entries") tried to make MTD related debugfs stuff consistent across the
> MTD framework by creating a root <debugfs>/mtd/ directory containing
> one directory per MTD device.
>
> The problem is that, by default, the MTD layer only registers the
> master device if no partitions are defined for this master. This
> behavior breaks all drivers that expect mtd->dbg.dfs_dir to be filled
> correctly after calling mtd_device_register() in order to add their own
> debugfs entries.
>
> The only way we can force all MTD masters to be registered no matter if
> they expose partitions or not is by enabling the
> CONFIG_MTD_PARTITIONED_MASTER option.
>
> In such situations, there's no other solution but to accept skipping
> debugfs initialization when dbg.dfs_dir is invalid, and when this
> happens, inform the user that he should consider enabling
> CONFIG_MTD_PARTITIONED_MASTER.
>
> Fixes: e8e3edb95ce6 ("mtd: create per-device and module-scope debugfs entries")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Mario J. Rugiero <mrugiero@xxxxxxxxx>
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/mtd/devices/docg3.c | 7 ++++++-
> drivers/mtd/nand/nandsim.c | 12 +++++++++---
> 2 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index 84b16133554b..0806f72102c0 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -1814,8 +1814,13 @@ static void __init doc_dbg_register(struct mtd_info *floor)
> struct dentry *root = floor->dbg.dfs_dir;
> struct docg3 *docg3 = floor->priv;
>
> - if (IS_ERR_OR_NULL(root))
> + if (IS_ERR_OR_NULL(root)) {
> + if (IS_ENABLED(CONFIG_DEBUG_FS) &&
> + !IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
> + dev_warn(floor->dev.parent,
> + "CONFIG_MTD_PARTITIONED_MASTER must be enabled to expose debugfs stuff\n");
> return;
> + }
>
> debugfs_create_file("docg3_flashcontrol", S_IRUSR, root, docg3,
> &flashcontrol_fops);
> diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
> index 246b4393118e..a22f4d7ca1cb 100644
> --- a/drivers/mtd/nand/nandsim.c
> +++ b/drivers/mtd/nand/nandsim.c
> @@ -520,11 +520,17 @@ static int nandsim_debugfs_create(struct nandsim *dev)
> struct dentry *root = nsmtd->dbg.dfs_dir;
> struct dentry *dent;
>
> - if (!IS_ENABLED(CONFIG_DEBUG_FS))
> - return 0;
> + if (IS_ENABLED(CONFIG_DEBUG_FS) &&
> + !IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER) &&
> + dev->nbparts)
> + NS_WARN("CONFIG_MTD_PARTITIONED_MASTER must be enabled to expose debugfs stuff\n");
>
> + /*
> + * Just skip debugfs initialization when the debugfs directory is
> + * missing.
> + */
> if (IS_ERR_OR_NULL(root))
> - return -1;
> + return 0;
>
> dent = debugfs_create_file("nandsim_wear_report", S_IRUSR,
> root, dev, &dfs_fops);