From mboxrd@z Thu Jan 1 00:00:00 1970 From: vikashskumar@gmail.com (Vikash Kumar) Date: Mon, 9 May 2011 17:36:30 +0530 Subject: char driver error In-Reply-To: References: Message-ID: To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org 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 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 > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies at kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20110509/bb14720f/attachment.html