From: <rdq@metamail.co>
To: <kernelnewbies@kernelnewbies.org>
Subject: debugfs question ...
Date: Tue, 30 Apr 2019 12:45:08 +0100 [thread overview]
Message-ID: <009001d4ff4a$2ac6a030$8053e090$@metamail.co> (raw)
Greetings,
My I2C sensor driver has a debugfs entry for development purposes.
Everything works fine with the exception of the read operation. When 'cat'
is used, the read operation is called repeatedly and indefinitely. If the
read() is changed to return 0 then, as expected, nothing is displayed.
The pattern for the implementation is (AFAICT) right out of the book (shown
below).
What am I missing? Any thoughts much appreciated.
TAIA.
RDQ
static ssize_t sc031gs_reg_read_file(struct file *file, char __user
*user_buf,
size_t count, loff_t *ppos)
{
char *buf = 0;
ssize_t total = 0;
struct sc031gs_dev *sensor = file->private_data;
if (!sensor)
return -EINVAL;
if (*ppos < 0 || !count)
return -EINVAL;
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
total = snprintf(buf,count,"Hello world\n");
if (total >= 0) {
if (copy_to_user(user_buf, buf, total)) {
kfree(buf);
return -EFAULT;
}
*ppos += total;
}
kfree(buf);
return total;
}
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
next reply other threads:[~2019-04-30 11:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-30 11:45 rdq [this message]
2019-04-30 12:07 ` debugfs question Greg KH
[not found] ` <014a01d50028$ce098580$6a1c9080$@metamail.co>
2019-05-01 14:35 ` 'Greg KH'
2019-04-30 12:11 ` Martin Christian
2019-05-01 12:06 ` rdq
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='009001d4ff4a$2ac6a030$8053e090$@metamail.co' \
--to=rdq@metamail.co \
--cc=kernelnewbies@kernelnewbies.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).