On Thu, Jun 25, 2009 at 11:12 AM, Shakthi Kannan <shakthim...@gmail.com>wrote:
> Hi, > > --- On Wed, Jun 24, 2009 at 11:39 AM, paras<bepa...@gmail.com> wrote: > | int ret, val; > | > | printk(KERN_INFO "Entering Function %s \n", __FUNCTION__); > | > | ret = copy_from_user(&val, buffer, length); > \-- > > 'val' can be used as 'char *' buffer. > > --- > | / # echo 1 > /proc/test/mychrdev1 > | Entering Function mychrdev_proc_write > | val = 822738944 > \-- > > 1. echo by default adds a \n in the output. So, if you printk the > length value in your code, you will get length as '2'. To suppress the > newline and just get '1' in the above, you should use: > > echo -n 1 > /proc/test/mychrdev1 > > 2. You should initialize your local variables, val, and ret to zero. > > If you do printk %d, %x on val for the above, it will print '49' and > '31' respectively. They are the decimal and hexadecimal equivalents of > the character '1' that has been passed. > > Also refer, 'Access the Linux kernel using the /proc filesystem': > http://www.ibm.com/developerworks/linux/library/l-proc.html > > Not sure why you want to use /proc, as /sysfs is used in 2.6. > > SK > Thank you for great support. I want to add one more point in this. we can replace copy_from_user with sscanf . e.g.Try Replacing.. ret = copy_from_user(&val, buffer, length); if(ret < 0) { printk(KERN_INFO "copy_from_user fail\n"); } with *sscanf(buffer, "%d", &val);* > > -- > Shakthi Kannan > http://www.shakthimaan.com > > _______________________________________ > Pune GNU/Linux Users Group Mailing List _______________________________________ Pune GNU/Linux Users Group Mailing List
