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    SubjectRe: [PATCH] debugfs: add helper function to create device related seq_file
    On 10/11/14 18:01, Arend van Spriel wrote:
    > This patch adds a helper function that simplifies adding a
    > sequence file for device drivers. The calling device driver
    > needs to provide a read function and a device pointer. The
    > field struct seq_file::private will reference the device
    > pointer upon call to the read function so the driver can
    > obtain his data from it and do its seq_printf() calls.

    Maybe should have made this RFC first. Anyways, it is intended for 3.19,
    although I don't mind if it would end up in 3.18 :-p

    Regards,
    Arend

    > Signed-off-by: Arend van Spriel<arend@broadcom.com>
    > ---
    > fs/debugfs/file.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
    > include/linux/debugfs.h | 16 ++++++++++++++-
    > 2 files changed, 69 insertions(+), 1 deletion(-)
    >
    > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
    > index 76c08c2..088b3fc 100644
    > --- a/fs/debugfs/file.c
    > +++ b/fs/debugfs/file.c
    > @@ -22,6 +22,7 @@
    > #include<linux/io.h>
    > #include<linux/slab.h>
    > #include<linux/atomic.h>
    > +#include<linux/device.h>
    >
    > static ssize_t default_read_file(struct file *file, char __user *buf,
    > size_t count, loff_t *ppos)
    > @@ -761,3 +762,56 @@ struct dentry *debugfs_create_regset32(const char *name, umode_t mode,
    > EXPORT_SYMBOL_GPL(debugfs_create_regset32);
    >
    > #endif /* CONFIG_HAS_IOMEM */
    > +
    > +struct debugfs_devm_entry {
    > + int (*read)(struct seq_file *seq, void *data);
    > + struct device *dev;
    > +};
    > +
    > +static int debugfs_devm_entry_open(struct inode *inode, struct file *f)
    > +{
    > + struct debugfs_devm_entry *entry = inode->i_private;
    > +
    > + return single_open(f, entry->read, entry->dev);
    > +}
    > +
    > +static const struct file_operations debugfs_devm_entry_ops = {
    > + .owner = THIS_MODULE,
    > + .open = debugfs_devm_entry_open,
    > + .release = single_release,
    > + .read = seq_read,
    > + .llseek = seq_lseek
    > +};
    > +
    > +/**
    > + * debugfs_create_devm_seqfile - create a debugfs file that is bound to device.
    > + *
    > + * @dev: device related to this debugfs file.
    > + * @name: name of the debugfs file.
    > + * @parent: a pointer to the parent dentry for this file. This should be a
    > + * directory dentry if set. If this parameter is %NULL, then the
    > + * file will be created in the root of the debugfs filesystem.
    > + * @read_fn: function pointer called to print the seq_file content.
    > + */
    > +struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
    > + struct dentry *parent,
    > + int (*read_fn)(struct seq_file *s,
    > + void *data))
    > +{
    > + struct debugfs_devm_entry *entry;
    > +
    > + if (IS_ERR(parent))
    > + return ERR_PTR(-ENOENT);
    > +
    > + entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
    > + if (!entry)
    > + return ERR_PTR(-ENOMEM);
    > +
    > + entry->read = read_fn;
    > + entry->dev = dev;
    > +
    > + return debugfs_create_file(name, S_IRUGO, parent, entry,
    > + &debugfs_devm_entry_ops);
    > +}
    > +EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);
    > +
    > diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
    > index 4d0b4d1..f8c0db4 100644
    > --- a/include/linux/debugfs.h
    > +++ b/include/linux/debugfs.h
    > @@ -99,13 +99,18 @@ struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
    > struct dentry *parent,
    > u32 *array, u32 elements);
    >
    > +struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
    > + struct dentry *parent,
    > + int (*read_fn)(struct seq_file *s,
    > + void *data));
    > +
    > bool debugfs_initialized(void);
    >
    > #else
    >
    > #include<linux/err.h>
    >
    > -/*
    > +/*
    > * We do not return NULL from these functions if CONFIG_DEBUG_FS is not enabled
    > * so users have a chance to detect if there was a real error or not. We don't
    > * want to duplicate the design decision mistakes of procfs and devfs again.
    > @@ -251,6 +256,15 @@ static inline struct dentry *debugfs_create_u32_array(const char *name, umode_t
    > return ERR_PTR(-ENODEV);
    > }
    >
    > +static inline struct dentry *debugfs_create_devm_seqfile(struct device *dev,
    > + const char *name,
    > + struct dentry *parent,
    > + int (*read_fn)(struct seq_file *s,
    > + void *data))
    > +{
    > + return ERR_PTR(-ENODEV);
    > +}
    > +
    > #endif
    >
    > #endif



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