Bryan Burnett's configuration for his SNES controller on his Raspberry Pi MAME:
Edit individual config files
Global config file
input_player1_joypad_index = "0"
input_player1_b_btn = "2"
input_player1_y_btn = "3"
input_player1_select_btn = "8"
input_player1_start_btn = "9"
input_player1_up_axis = "-1"
input_player1_down_axis = "+1"
input_player1_left_axis = "-0"
input_player1_right_axis = "+0"
input_player1_a_btn = "1"
input_player1_x_btn = "0"
input_player1_l_btn = "4"
input_player1_r_btn = "5"
input_enable_hotkey_btn = 8
input_exit_emulator_btn = 9
input_menu_toggle_btn = 5
input_player2_joypad_index = "0"
input_player2_b_btn = "2"
input_player2_y_btn = "3"
input_player2_select_btn = "8"
input_player2_start_btn = "9"
input_player2_up_axis = "-1"
input_player2_down_axis = "+1"
input_player2_left_axis = "-0"
input_player2_right_axis = "+0"
input_player2_a_btn = "1"
input_player2_x_btn = "0"
input_player2_l_btn = "4"
input_player2_r_btn = "5"
NES config file
input_menu_toggle_btn = 5
input_enable_hotkey_btn = 8
input_exit_emulator_btn = 9
input_player1_a_btn = 2
input_player1_b_btn = 3
input_player1_y_btn = 0
input_player1_x_btn = 1
input_player1_start_btn = 9
input_player1_select_btn = 8
input_player1_l_btn = 4
input_player1_r_btn = 5
input_player1_left_axis = -0
input_player1_right_axis = +0
input_player1_up_axis = -1
input_player1_down_axis = +1
input_player2_a_btn = 2
input_player2_b_btn = 3
input_player2_y_btn = 0
input_player2_x_btn = 1
input_player2_start_btn = 9
input_player2_select_btn = 8
input_player2_l_btn = 4
input_player2_r_btn = 5
input_player2_left_axis = -0
input_player2_right_axis = +0
input_player2_up_axis = -1
input_player2_down_axis = +1
SNES config file
input_menu_toggle_btn = 5
input_enable_hotkey_btn = 8
input_exit_emulator_btn = 9
input_player1_a_btn = 1
input_player1_b_btn = 2
input_player1_y_btn = 3
input_player1_x_btn = 0
input_player1_start_btn = 9
input_player1_select_btn = 8
input_player1_l_btn = 4
input_player1_r_btn = 5
input_player1_left_axis = -0
input_player1_right_axis = +0
input_player1_up_axis = -1
input_player1_down_axis = +1
input_player2_a_btn = 1
input_player2_b_btn = 2
input_player2_y_btn = 3
input_player2_x_btn = 0
input_player2_start_btn = 9
input_player2_select_btn = 8
input_player2_l_btn = 4
input_player2_r_btn = 5
input_player2_left_axis = -0
input_player2_right_axis = +0
input_player2_up_axis = -1
input_player2_down_axis = +1
DGEN config file
input_menu_toggle_btn = 5
input_enable_hotkey_btn = 8
input_exit_emulator_btn = 9