On 09/05/2021 22:39:30-0500, Samuel Holland wrote: > On 4/30/21 4:02 AM, Maxime Ripard wrote: > > Hi, > > > > On Sun, Apr 18, 2021 at 08:45:49PM -0500, Samuel Holland wrote: > >> The sun6i RTC provides 32 bytes of general-purpose data registers. > >> They can be used to save data in the always-on RTC power domain. > >> The registers are writable via 32-bit MMIO accesses only. > >> > >> Expose the region as a NVMEM provider so it can be used by userspace and > >> other drivers. > >> > >> Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx> > > > > As far as I understood, you want to use those registers to implement > > super-standby? If so, while it makes sense for the kernel to be able to > > be able to write to those registers, I guess it would be a bit unwise to > > allow the userspace to access it? > > I want the user to be able to pass information to the bootloader (to > select a boot device, e.g. reboot to FEL). I also want the user to be > able to read data stored to these registers by system firmware (e.g. > crust writes exception information there). It's not really related to > standby. > > I would want to stack a nvmem-reboot-mode on top to give friendlier > names to some of the numbers, but I don't see a problem with root having > direct access to the registers. It's no different from /dev/nvram > providing access to the PC CMOS RAM. > (which is deprecated in favor of nvmem) -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
