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SubjectRe: [PATCH next 3/3] debugfs: introduce debugfs_create_seq[,_data]
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On 2019/11/29 22:22, Greg KH wrote:
> On Fri, Nov 29, 2019 at 05:27:52PM +0800, Kefeng Wang wrote:
>> Like proc_create_seq[,_data] in procfs, introduce a similar
>> debugfs_create_seq[,_data] function, which could drastically
>> reduces the boilerplate code.
>>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>> fs/debugfs/file.c | 62 ++++++++++++++++++++++++++++++++++++++++-
>> include/linux/debugfs.h | 16 +++++++++++
>> 2 files changed, 77 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
>> index 68f0c4b19bef..77522717c9fb 100644
>> --- a/fs/debugfs/file.c
>> +++ b/fs/debugfs/file.c
>> @@ -1107,7 +1107,10 @@ EXPORT_SYMBOL_GPL(debugfs_create_regset32);
>> #endif /* CONFIG_HAS_IOMEM */
>>
>> struct debugfs_entry {
>> - int (*read)(struct seq_file *seq, void *data);
>> + union {
>> + const struct seq_operations *seq_ops;
>> + int (*read)(struct seq_file *seq, void *data);
>> + };
>> void *data;
>> };
>>
>> @@ -1196,3 +1199,60 @@ struct dentry *debugfs_create_single_data(const char *name, umode_t mode,
>> &debugfs_entry_ops);
>> }
>> EXPORT_SYMBOL_GPL(debugfs_create_single_data);
>> +
>> +static int debugfs_entry_seq_open(struct inode *inode, struct file *file)
>> +{
>> + struct debugfs_entry *entry = inode->i_private;
>> + int ret;
>> +
>> + entry = debugfs_clear_lowest_bit(entry);
>> +
>> + ret = seq_open(file, entry->seq_ops);
>> + if (!ret && entry->data) {
>> + struct seq_file *seq = file->private_data;
>> + seq->private = entry->data;
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static const struct file_operations debugfs_seq_fops = {
>> + .open = debugfs_entry_seq_open,
>> + .read = seq_read,
>> + .llseek = seq_lseek,
>> + .release = seq_release,
>> +};
>> +
>> +/**
>> + * debugfs_create_seq_data - create a file in the debugfs filesystem
>> + * @name: a pointer to a string containing the name of the file to create.
>> + * @mode: the permission that the file should have.
>> + * @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.
>> + * @data: a pointer to something that the caller will want to get to later
>> + * on. The inode.i_private pointer will point to this value on
>> + * the open() call.
>> + * @seq_ops: seq_operations pointer of the seqfile.
>> + *
>> + * This function creates a file in debugfs with the extra data and a seq_ops.
>> + */
>> +struct dentry *debugfs_create_seq_data(const char *name, umode_t mode,
>> + struct dentry *parent, void *data,
>> + const struct seq_operations *seq_ops)
>> +{
>> + struct debugfs_entry *entry;
>> +
>> + entry = kzalloc(sizeof(*entry), GFP_KERNEL);
>> + if (!entry)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + entry->seq_ops = seq_ops;
>> + entry->data = data;
>> +
>> + entry = debugfs_set_lowest_bit(entry);
>> +
>> + return debugfs_create_file(name, mode, parent, entry,
>> + &debugfs_seq_fops);
>> +}
>> +EXPORT_SYMBOL_GPL(debugfs_create_seq_data);
>> diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
>> index 82171f183e93..d32d49983547 100644
>> --- a/include/linux/debugfs.h
>> +++ b/include/linux/debugfs.h
>> @@ -147,6 +147,10 @@ struct dentry *debugfs_create_single_data(const char *name, umode_t mode,
>> int (*read_fn)(struct seq_file *s,
>> void *data));
>>
>> +struct dentry *debugfs_create_seq_data(const char *name, umode_t mode,
>> + struct dentry *parent, void *data,
>> + const struct seq_operations *seq_ops);
>> +
>> bool debugfs_initialized(void);
>>
>> ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf,
>
> If you notice, I have been removing the return value of the
> debugfs_create_* functions over the past few kernel versions (look at
> 5.5-rc1 for a lot more). Please don't add any new functions that also
> return a dentry that I then need to go and remove.

Hi Greg, see function debugfs_create_seq_data()and debugfs_create_single_data(),
they are wrapper function of debugfs_create_file(), when remove the debugfs file
called debugfs_remove(), some drivers could do such thing, we must return a dentry
to the caller.

>
> Just have these be void functions, no need to return anything.
>
> thanks,
>
> greg k-h
>
> .
>

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