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Linux - Embedded & Single-board computer This forum is for the discussion of Linux on both embedded devices and single-board computers (such as the Raspberry Pi, BeagleBoard and PandaBoard). Discussions involving Arduino, plug computers and other micro-controller like devices are also welcome.

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Old 05-20-2018, 02:34 PM   #1
Jim232
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memory mapping using /dev/mem versus /dev/gpiomem ?


Per doc /dev/mem usage requires "root" "privileges.
Also per doc /dev/gpiomem no "root privileges " are necessary since "Linux will take care of privileges".
I am not sure my complier is smart enough to stop me from opening the /dev/mem if my app has no root privileges. My app does not fully run so at this point I do not know that.

For now I can open both /dev/mem and /dev/gpiomem.
Since it appears that I can use both , therefore my question to the forum is
which /dev is more appropriate to use to access RPi hardware.
 
Old 05-20-2018, 04:13 PM   #2
jlinkels
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/dev/gpiomem

It is your program which decides to use which /dev/xxx. There is no automatic choice. Unless you use some development library or framework and have not told us. Libraries often offer functions which encapsulate access to /dev/xxx. So you don't see which device is used.

IIRC Python offers a library with functions to read/write GPIO. It doesn't tell you, but if /dev/gpiomem is available it uses /dev/gpiomem. If it is not available it reverts to /dev/mem and you need to run the program with root privileges.

Not 100%, I access GPIO with Tcl.

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