Re: [PATCH 0/2] ARM: Expose Raspberry Pi revision code in /proc/cpuinfo

["J. Neuschäfer" <j.neuschaefer@gmx.net>]

On Mon, Jul 08, 2024 at 06:14:01PM +0200, Stefan Wahren wrote:
> Hi Jonathan,
>
> Am 08.07.24 um 01:08 schrieb Jonathan Neuschäfer:
> > Raspberry Pi boards have a "revision code", documented here:
> >
> >    https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#new-style-revision-codes
> AFAIK these revision codes mostly refer to the board and not to the CPU.

True.

> The abuse of /proc/cpuinfo has been rejected in the past and from my
> understanding this applies also in this case.

Alright

> > This patch copies what the downstream kernel does and reads it from the
> > devicetree property /system/linux,revision. This enables some software
> > to work as intended on mainline kernels:
> >
> >    https://github.com/hzeller/rpi-rgb-led-matrix/blob/a3eea997a9254b83ab2de97ae80d83588f696387/lib/gpio.cc#L247
> This is a bad example because the application doesn't really care about
> the kernel and directly access the hardware registers via /dev/mem. A
> proper application would use the dedicated userspace API (GPIO Character
> Device or PWM).

Right

> I would bet that the application does not work with the Raspberry Pi 5.

Probably, yeah.


Jonathan