LinuxQuestions.org - How can I make device driver for llseek.

I've made read/write function for device driver emulator like nvram or flash ram using memory buffer.(call it nvram emul driver)
Total buffer size is 1024

Total read/ total write is ok.
But, problem is llseek.

I don't know how I can use the specific positon for read/write function using llseek.
I think that offset is very important value for llseek.
But, I don't know or I don't understand how I can use it.

How can I use specific positon for llseek based on my read/write driver.

Do I need to fix ? or modify in detail?

Code:

#define  BUFF_SIZE      1024



ssize_t ram_emul_read(uint32_t partition_id, char * buf, size_t count, loff_t  offset)

{

    copy_to_user(buf,memory_buffer,count);

    return count;

}



ssize_t ram_emul_write( uint32_t partition_id, const char * buf, size_t count, loff_t offset)

{



    if (BUFF_SIZE < count)

        sz_data  = BUFF_SIZE;

    sz_data  = count;



    memcpy(memory_buffer,buf,sz_data);

    return count;

}



===============================



lseek function

-->



    switch (whence)

    {

        case 0: /* SEEK_SET */

            newpos = off;

            break;

        case 1: /* SEEK_CUR */

            newpos = filep->f_pos + off;

            break;

        case 2: /* SEEK_END */

            newpos = ram_emul_get_partition_size(device->id) + off;

            break;

        default:    /* shouldn't happen */

            // Unlock and return error

            up(&nvram_mutex);

            TRACE_END_ERR("Failed, invalid WHENCE parameter");

            return -EINVAL;

    }





int ram_emul_get_partition_size(uint32_t partition_id)

{



    return BUFF_SIZE;

}