Re: Making VDR run under Systemd

Mon, Oct 11, 2021 at 04:02:43PM +0100, Richard F wrote:
>Powersaving for DVB receivers - try the attached patch from glenvt18

Thank you. I will test it later once I have hooked up the Raspberry Pi 
to my laboratory power supply so that I can observe the total power 
consumption.

While "uhubctl -a off" would cause an optimal mouse to power off its 
LED, it will not completely cut the power. I tested this by plugging in 
a mobile phone to the USB port. It indicated that charging is available.

One impact of "uhubctl -a off" is that any plug/unplug events for the 
affected ports will be disabled, and "lsusb" will reflect the state as 
it was before the invocation.

I just confirmed with a laboratory power supply that my USB DVB-T/T2/C 
stick is consuming 61 mA at 5 volts. If I remember correctly, USB 
devices are allowed to drain up to 100 mA without any negotiation, so it 
should not be out-of-spec. Those additional 0.35 watts should be a 
significant portion of the total power consumption. I did not measure 
yet, but I hope it to be in the range of 2 to 3 watts.

For my use case, I think that I will only configure udev events for 
inserting or removing the stick. No shutdown command would be configured 
in VDR. I would abruptly shut down VDR and lircd by unplugging the 
adapter. They would observe the abrupt loss of DVB hardware, followed by 
a terminating signal sent by systemd or udevd.

Best regards,

	Marko

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