Updated README.md file with some installation problems solution.

README.md

@@ -40,6 +40,111 @@ Find your kernel source tree, and edit `src/Makefile`. Locate the following line
 Modify this line so that it points to the correct source tree.
 After that, run `make` to create `fl2000.ko` and run `insmod fl2000.ko` to load the driver.
 
+
+**Note:**
+
+- If you miss some program (like 'flex'), just do 
+
+  ```
+  $ sudo apt-get install _program_name_
+  ```  
+
+  to get it.
+
+- If you get some errors in `insmod` command like:
+
+  - **"Key was rejected by service":** You are working in Secure Boot, so you have to sign the `fl2000.ko` module. 
+
+    1. Create `openssl.conf` file with this text inside (under `req_distinguished_name` you can edit the fields with custom preference, but it's optional):
+
+    ```
+    # This definition stops the following lines choking if HOME isn't
+    # defined.
+    HOME                    = .
+    RANDFILE                = $ENV::HOME/.rnd 
+    [ req ]
+    distinguished_name      = req_distinguished_name
+    x509_extensions         = v3
+    string_mask             = utf8only
+    prompt                  = no
+
+    [ req_distinguished_name ]
+    countryName             = CA
+    stateOrProvinceName     = Quebec
+    localityName            = Montreal
+    0.organizationName      = cyphermox
+    commonName              = Secure Boot Signing
+    emailAddress            = [email protected]
+
+    [ v3 ]
+    subjectKeyIdentifier    = hash
+    authorityKeyIdentifier  = keyid:always,issuer
+    basicConstraints        = critical,CA:FALSE
+    extendedKeyUsage        = codeSigning,1.3.6.1.4.1.311.10.3.6,1.3.6.1.4.1.2312.16.1.2
+    nsComment               = "OpenSSL Generated Certificate"
+    ```
+
+    2. Now, create public and private keys using openssl command as:
+
+    ```
+    $ openssl req -config openssl.conf -new -x509 -newkey rsa:2048 -nodes -days 36500 -outform DER -keyout "MOK.priv" -out "MOK.der"
+    ```
+
+    This command, will create the “MOK.priv” and “MOK.der” files in present working directory (PWD) by accepting openssl.conf as input file.
+
+    3. Now, the next step is to enroll this keys with the SHIM UEFI Bootloader ( SHIM is a simple software package that is designed to work as a first-  
+       stage bootloader on UEFI systems ) . This enrolling can be done as:
+
+    ```
+    $ sudo mokutil --import MOK.der
+    ```
+
+    Then you should input password and confirm it. Remember the password you entered here, as we would need to add this when we reboot the 
+    machine.
+
+    4. Now reboot and at start press "Enroll MOK", then "Enroll the keys", now press "Yes", "Continue", "Yes" again, enter the password 
+       inserted in the step before and then reboot again.
+
+    5. Now, after your Linux machine is rebooted completely, lets go back to signing the kernel module and try to insert it:
+
+    ```
+    $ kmodsign sha512 MOK.priv MOK.der fl2000.ko
+    ```
+
+    6. Now retry with the insmod command and if you have another error message, go to its description.
+
+  - **"Invalid module format":** You have compiled the fl2000.ko module with the wrong linux-headers version or you have not installed it well.
+
+    1. Check that the actual version in use by the sistem is the same you have written in the KERNEL_PATH variable:
+
+    ```
+    $ uname -r
+    ```
+
+    2. If it's not the same, then change it, do `$ make clean`, then `$ make`, resign with `kmodsign` (if needed) and redo the `insmod` command.
+
+    3. If it is the same, you need to uninstall and reinstall it, so you have to follow these steps:
+
+    ```
+    $ sudo apt update && sudo apt upgrade
+    $ sudo apt remove --purge linux-headers-*
+    $ sudo apt autoremove && sudo apt autoclean
+    $ sudo apt install linux-headers-generic
+    ```
+
+    4. If the last "generic" version hasn't been installed, try to install it manually by:
+
+    ```
+    $ sudo apt-get install linux-headers- 
+    ```
+
+    press `TAB`, look to the greater "-generic" version, install it and `reboot`.
+
+    5. Now write in the ./FL2000/src/Makefile into the `KERNEL_PATH` variable the right linux-headers generic version and redo the steps to insmod.
+
+  - **"Bad message":** You have generated the `fl2000.ko` module, in a wrong way. Try to check every steps and commands.
+
+
 #### 6b. Test the driver
 
 In the `sample` folder, run `make` to create `fltest`. If you you are using a
@@ -51,9 +156,25 @@ user mode buffer access methods (e.g  copy to kernel internal buffer, or
 directly locking down user buffer). Look at `fl2000_ioctl.h` for detailed
 information.
 
+
+**Note:**
+
+If something goes wrong (like it cannot find the device) check the right name of the device in `/dev/` directory (for example could be "fl2000-2") and edit it in `./FL2000/sample/main.c` file in the line:
+
+ ```
+ #define	FL2K_NAME	"/dev/fl2000-2"
+ ```
+
+Then delete `fltest` file if it is present and do:
+
+ ```
+ $ sudo make fltest
+ ```
+
+Retry to run `./fltest 0`
+
 ### 7. How do I file a bug to the Fresco Logic developers?
 
 You can file bugs to [Github Issues](https://github.com/fresco-fl2000/fl2000/issues)
 
 
-