Must run as root to be able to access /dev/mem when using together with Flask

[jghaanstra]

I'm trying to built a simple WebAPI with Flask for controlling my LED matrix. Controlling the LED matrix with the Python API works just fine. But when I add the code for Flask to create the endpoints I get the following error.

 * Serving Flask app "python-led-matrix-api" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://0.0.0.0:5050/ (Press CTRL+C to quit)
 * Restarting with stat
Must run as root to be able to access /dev/mem
Prepend 'sudo' to the command

I dont understand why using Flask together with rpi-rgb-led-matrix would generate this error. My code looks like this (beware, I'm a python newbie)

from flask import Flask, request, jsonify
from flask_restful import Resource, Api
from rgbmatrix import RGBMatrix, RGBMatrixOptions, graphics
import time

app = Flask(__name__)
api = Api(app)

options = RGBMatrixOptions()
options.hardware_mapping = 'adafruit-hat'
options.rows = 64
options.cols = 64
options.chain_length = 1
options.parallel = 1
options.row_address_type = 0
options.multiplexing = 0
options.pwm_bits = 11
options.brightness = 100
options.pwm_lsb_nanoseconds = 130
options.led_rgb_sequence = 'RGB'
options.gpio_slowdown = 1

matrix = RGBMatrix(options = options)
offscreen_canvas = matrix.CreateFrameCanvas()

# FUNCTIONS
def RunText(textfont, xpos, ypos, r, g, b, text):
    font = graphics.Font()
    font.LoadFont(textfont)
    textColor = graphics.Color(r, g, b)

    offscreen_canvas.Clear()
    len = graphics.DrawText(offscreen_canvas, font, xpos, ypos, textColor, text)
    xpos -= 1
    if (xpos + len < 0):
        xpos = offscreen_canvas.width

    time.sleep(0.05)
    offscreen_canvas = matrix.SwapOnVSync(offscreen_canvas)

def Fill(r, g, b):
    offscreen_canvas.Clear()
    offscreen_canvas.Fill(r, g, b)
    offscreen_canvas = matrix.SwapOnVSync(offscreen_canvas)

# ENDPOINTS
class runText(Resource):
    def post(self):
        json = request.get_json()
        #p = subprocess.Popen(['python', './library/runtext.py', '--led-rows', '64', '--led-cols', '64'])
        RunText(json['font'], json['position']['x'], json['position']['y'], json['color']['r'], json['color']['g'], json['color']['b'], json['text'])

        return jsonify({"success": True})

class fillColor(Resource):
    def post(self):
        json = request.get_json()
        #p = subprocess.Popen(['python', './library/fill.py', '--led-rows', '64', '--led-cols', '64', '-r', '255', '-g', '0', '-b', '0'])
        Fill(json['color']['r'], json['color']['g'], json['color']['b'])

        return jsonify({"success": True})

class Clear(Resource):
    def get(self):
        p = subprocess.Popen(['python', './library/clear.py', '--led-rows', '64', '--led-cols', '64'])

        return jsonify({"success": True})

api.add_resource(runText, '/text')
api.add_resource(fillColor, '/fill')
api.add_resource(Clear, '/clear')

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5050, debug=True)

[hzeller]

You always have to run as root to generate proper images ( https://github.com/hzeller/rpi-rgb-led-matrix#running-as-root )

That being said, since recently (a couple of days ago), it it also possible to run without root, but it will be degraded performance, so it is still not desired.

[jghaanstra]

Thanx for the quick response @hzeller . I forgot to mention that I'm running as root already.

pi@raspberrypi3bplus:~/python-led-matrix $ sudo su
root@raspberrypi3bplus:/home/pi/python-led-matrix# sudo python python-led-matrix-api.py
 * Serving Flask app "python-led-matrix-api" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://0.0.0.0:5050/ (Press CTRL+C to quit)
 * Restarting with stat
Must run as root to be able to access /dev/mem
Prepend 'sudo' to the command
root@raspberrypi3bplus:/home/pi/python-led-matrix#

[hzeller]

did you compile from a recent version if the library? Hardware detection of the Pi3+ was not working before unless you manually edited the code.

[hzeller]

do you drop privileges anywhere in your flask app before initializing the rgb matrix? try starting it as early as possible, before starting flask, which might do privilege dropping.

[jghaanstra]

I used the outdated script from Adafruit but adjusted it to the latest commit so it should be pretty up to date.

But I left for holidays this morning. So I will check in three weeks ago again and post back here.

[angelogoncalve]

Add this options when you are creating the list of options that have the matrix/panel/display:

options.drop_privileges = 0 options.daemon = 0

[jghaanstra]

Add this options when you are creating the list of options that have the matrix/panel/display:

options.drop_privileges = 0 options.daemon = 0

Thanx, this did the trick!