On Fri, Sep 10, 2010 at 05:51:41PM +0200, fabio de francesco wrote:
>
> static ssize_t
> mycdrv_read (struct file *file, char __user * buf, size_t lbuf, loff_t * ppos)
> {
> int nbytes, maxbytes, bytes_to_do;
> maxbytes = KBUF_SIZE - *ppos;
> bytes_to_do = lbuf <= maxbytes ? lbuf : maxbytes;
> nbytes = lbuf - copy_to_user (buf, kbuf + *ppos, bytes_to_do);
> *ppos += nbytes;
> printk (KERN_INFO "\n READING function, nbytes=%d, pos=%d\n", nbytes,
> (int)*ppos);
> return nbytes;
> }
I'm not going to flat out answer your query, but help you work towards
the solution yourself.
Think about the termination case. In order to terminate, you'll need to
return 0 to signal an end of file to the user-mode read.
In what case could your code return 0?
--
-joshc
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