Re: [PATCH v4 1/2] mtd: mtdcore: add debugfs nodes for querying the flash name and id

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 30 May 2019 23:21:00 +0800
Zhuohao Lee <zhuohao@chromium.org> wrote:

> Currently, we don't have vfs nodes for querying the underlying flash name
> and flash id. This information is important especially when we want to
> know the flash detail of the defective system. In order to support the
> query, we add mtd_debugfs_populate() to create two debugfs nodes
> (ie. partname and partid). The upper driver can assign the pointer to
> partname and partid before calling mtd_device_register().
> 
> Signed-off-by: Zhuohao Lee <zhuohao@chromium.org>
> ---
> Changes in V4:
> - Separate the change to two patches. The first patch is adding the general
>   handling for the partname and partid in the mtdcore.c. The second patch
>   is enabling the two debugfs nodes for spi-nor.
> - Previous discussion: https://patchwork.ozlabs.org/patch/1097377/
> Changes in v3:
> - Add partname and partid to mtd.h and create debugfs inside mtdcore.c
> - Previous discussion: https://patchwork.ozlabs.org/patch/1095731/
> Changes in v2:
> - Change to use debugfs to output flash name and id
> - Previous discussion: https://patchwork.ozlabs.org/patch/1067763/
> ---
>  drivers/mtd/mtdcore.c   | 72 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/mtd/mtd.h |  4 +++
>  2 files changed, 76 insertions(+)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 3ef01baef9b6..b53b40cb2f04 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -357,6 +357,75 @@ static const struct device_type mtd_devtype = {
>  	.release	= mtd_release,
>  };
>  
> +static int mtd_partid_show(struct seq_file *s, void *p)
> +{
> +	struct mtd_info *mtd = s->private;
> +
> +	if (!mtd->dbg.partid)
> +		return 0;
> +
> +	seq_printf(s, "%s\n", mtd->dbg.partid);
> +
> +	return 0;
> +}
> +
> +static int mtd_partid_debugfs_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, mtd_partid_show, inode->i_private);
> +}
> +
> +static const struct file_operations mtd_partid_debug_fops = {
> +	.open           = mtd_partid_debugfs_open,
> +	.read           = seq_read,
> +	.llseek         = seq_lseek,
> +	.release        = single_release,
> +};
> +
> +static int mtd_partname_show(struct seq_file *s, void *p)
> +{
> +	struct mtd_info *mtd = s->private;
> +
> +	if (!mtd->dbg.partname)
> +		return 0;
> +
> +	seq_printf(s, "%s\n", mtd->dbg.partname);
> +
> +	return 0;
> +}
> +
> +static int mtd_partname_debugfs_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, mtd_partname_show, inode->i_private);
> +}
> +
> +static const struct file_operations mtd_partname_debug_fops = {
> +	.open           = mtd_partname_debugfs_open,
> +	.read           = seq_read,
> +	.llseek         = seq_lseek,
> +	.release        = single_release,
> +};
> +
> +static int mtd_debugfs_populate(struct mtd_info *mtd)
> +{
> +	struct dentry *root = mtd->dbg.dfs_dir;
> +	struct dentry *dent;
> +
> +	dent = debugfs_create_file("partid", S_IRUSR, root, mtd,
> +				   &mtd_partid_debug_fops);
> +	if (IS_ERR_OR_NULL(dent)) {
> +		pr_err("cannot create debugfs entry for partid\n");
> +		return -ENODEV;
> +	}
> +	dent = debugfs_create_file("partname", S_IRUSR, root, mtd,
> +				   &mtd_partname_debug_fops);
> +	if (IS_ERR_OR_NULL(dent)) {
> +		pr_err("cannot create debugfs entry for partname\n");
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
>  #ifndef CONFIG_MMU
>  unsigned mtd_mmap_capabilities(struct mtd_info *mtd)
>  {
> @@ -626,6 +695,9 @@ int add_mtd_device(struct mtd_info *mtd)
>  		if (IS_ERR_OR_NULL(mtd->dbg.dfs_dir)) {
>  			pr_debug("mtd device %s won't show data in debugfs\n",
>  				 dev_name(&mtd->dev));
> +		} else if (mtd_debugfs_populate(mtd)) {
> +			pr_debug("mtd device %s can't create debugfs\n",

						      s/create/populate/

Also, not sure we really need a dbg message here since you already have
error messages in mtd_debugfs_populate().

One last thing: can we move the debugfs_create_dir() call to
mtd_debugfs_populate() so all you have to do from add_mtd_device()
is call mtd_debugfs_populate().

Once addressed, you can add

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> +				 dev_name(&mtd->dev));
>  		}
>  	}
>  
> diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
> index 677768b21a1d..c20f53c77899 100644
> --- a/include/linux/mtd/mtd.h
> +++ b/include/linux/mtd/mtd.h
> @@ -203,6 +203,10 @@ struct module;	/* only needed for owner field in mtd_info */
>   */
>  struct mtd_debug_info {
>  	struct dentry *dfs_dir;
> +
> +	/* debugfs stuff starts here */
> +	const char *partname;
> +	const char *partid;
>  };
>  
>  struct mtd_info {


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