echo "minor number" > misc char driver - gets truncated - linux-kernel

Question

I have written a misc char driver and when I echo the minor number of the driver to misc character driver it does not receive the first digit.
The write function is like this,
static ssize_t hellowld_write(struct file *file, const char *buf,size_t len,
loff_t *ppos)
{
pr_debug("In hellowld_write len %d buf %s \n",len,buf);
minor[0] = '\0';
snprintf(minor, 20,"%d", hellowld_device.minor);
strncpy(inputminor, buf,len);
pr_debug("In hellowld_write -- minor %s -- recvNum %s end\n",minor, inputminor);
pr_debug("In hellowld_write -- strlen minor %d -- strlen inputminor %d end\n", strlen(minor), strlen(inputminor));
if( strncmp(minor, inputminor, strlen(minor)) == 0)
{
pr_debug("In hellowld_write -- strcmp passed \n");
return strlen(minor);
}
else
{
pr_debug("In hellowld_write -- strcmp failed \n");
return -EFAULT;
}
}
When I do,
echo "54" >/dev/hellowld
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] In hellowld_write len 1 buf
Dec 31 11:36:40 pavan-linux kernel: [16981.382424]
Dec 31 11:36:40 pavan-linux kernel: [16981.382424] o
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] In hellowld_write -- minor 54 -- recvNum
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] 4
Dec 31 11:36:40 pavan-linux kernel: [16981.382437] end
Dec 31 11:36:40 pavan-linux kernel: [16981.382444] In hellowld_write -- strlen minor 2 -- strlen inputminor 3 end
Dec 31 11:36:40 pavan-linux kernel: [16981.382448] In hellowld_write -- strcmp failed
echo "22" >/dev/hellowld
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] In hellowld_write len 3 buf 22
Dec 31 11:36:52 pavan-linux kernel: [16993.356993]
Dec 31 11:36:52 pavan-linux kernel: [16993.356993] o
Dec 31 11:36:52 pavan-linux kernel: [16993.357011] In hellowld_write -- minor 54 -- recvNum 22
Dec 31 11:36:52 pavan-linux kernel: [16993.357011] end
Dec 31 11:36:52 pavan-linux kernel: [16993.357017] In hellowld_write -- strlen minor 2 -- strlen inputminor 3 end
Dec 31 11:36:52 pavan-linux kernel: [16993.357021] In hellowld_write -- strcmp failed
why is that when I echo the minor number, the data received in the hellowld_write is truncated ?