char driver error

[Vikash Kumar]

Following are my observations from the code:

1) The driver is maintaining a 1 byte buffer.
memory_buffer = kmalloc(1, GFP_KERNEL);

2) Write operation always copies the last byte of user buffer to driver
buffer.
tmp=buf+count-1;
copy_from_user(memory_buffer,tmp,1)

3) Read operation always returns the copied character from driver buffer on
every read ignoring the count.
copy_to_user(buf,memory_buffer,1);

So, to me it seems everything is working fine.. what's the error here ? what
am I missing something?


Regards,
Vikash Kumar




On Mon, May 9, 2011 at 4:56 PM, Aravind Vijayan <aravind1123 at gmail.com>wrote:

> Hi all,
>       Let me begin this post with thanx all to whom help me on
> previous problem.I have completed jobs such as
> writing,making,inserting the  module.
>
> i create a character special file using mknod in /dev directory.
>
> i try to write data to my file by" echo -n "abcd" > /dev/memory "
>
> and when i try to read from that file i get  the last char was written
> to that file that is "d"
>
> here is my code:http://pastebin.com/9YsJetek
>
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