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    SubjectRe: [PATCH RESEND v2] char: misc:use DEFINE_PROC_SHOW_ATTRIBUTE micro to simplify misc proc_fops
    On Sun, Apr 10, 2022 at 03:16:27PM +0000, Junwen Wu wrote:
    > From: wujunwen <wudaemon@163.com>
    >
    > DEFINE_PROC_SHOW_ATTRIBUTE is used to simply seq_file flow ,so
    > we can use it to simplify misc proc_fops.
    >
    > Signed-off-by: wujunwen <wudaemon@163.com>
    > ---
    > V1 -> V2: Fix compile error with no "CONFIG_PROC_FS"
    >
    > drivers/char/misc.c | 41 ++++++++++++++---------------------------
    > 1 file changed, 14 insertions(+), 27 deletions(-)
    >
    > diff --git a/drivers/char/misc.c b/drivers/char/misc.c
    > index ca5141ed5ef3..076b7f08aa7a 100644
    > --- a/drivers/char/misc.c
    > +++ b/drivers/char/misc.c
    > @@ -64,40 +64,23 @@ static DEFINE_MUTEX(misc_mtx);
    > static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
    >
    > #ifdef CONFIG_PROC_FS
    > -static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
    > -{
    > - mutex_lock(&misc_mtx);
    > - return seq_list_start(&misc_list, *pos);
    > -}
    >
    > -static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
    > +static int misc_show(struct seq_file *seq, void *v)
    > {
    > - return seq_list_next(v, &misc_list, pos);
    > -}
    > + const struct miscdevice *p;
    >
    > -static void misc_seq_stop(struct seq_file *seq, void *v)
    > -{
    > + mutex_lock(&misc_mtx);
    > + list_for_each_entry(p, &misc_list, list) {
    > + seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
    > + }
    > mutex_unlock(&misc_mtx);
    > -}
    > -
    > -static int misc_seq_show(struct seq_file *seq, void *v)
    > -{
    > - const struct miscdevice *p = list_entry(v, struct miscdevice, list);
    > -
    > - seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
    > return 0;
    > }
    >
    > -
    > -static const struct seq_operations misc_seq_ops = {
    > - .start = misc_seq_start,
    > - .next = misc_seq_next,
    > - .stop = misc_seq_stop,
    > - .show = misc_seq_show,
    > -};
    > +DEFINE_PROC_SHOW_ATTRIBUTE(misc);
    > #endif
    >
    > -static int misc_open(struct inode *inode, struct file *file)
    > +static int misc_fops_open(struct inode *inode, struct file *file)
    > {
    > int minor = iminor(inode);
    > struct miscdevice *c;
    > @@ -148,7 +131,7 @@ static struct class *misc_class;
    >
    > static const struct file_operations misc_fops = {
    > .owner = THIS_MODULE,
    > - .open = misc_open,
    > + .open = misc_fops_open,
    > .llseek = noop_llseek,
    > };
    >
    > @@ -266,9 +249,11 @@ static char *misc_devnode(struct device *dev, umode_t *mode)
    > static int __init misc_init(void)
    > {
    > int err;
    > +#ifdef CONFIG_PROC_FS
    > struct proc_dir_entry *ret;
    >
    > - ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
    > + ret = proc_create("misc", 0, NULL, &misc_proc_ops);
    > +#endif

    Any way to do this without the #ifdef in the middle of the function?
    Otherwise it's not worth taking this change at all.

    thanks,

    greg k-h

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