Messages in this thread | | | Date | Fri, 30 Sep 2022 16:14:41 -0600 | From | Jack Rosenthal <> | Subject | Re: [PATCH v11] firmware: google: Implement cbmem in sysfs driver |
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On 2022-09-30 at 08:32 +0200, Greg KH wrote: > symlink? Ick, no, do not do that at all please. > > As these are device attributes, just stick with them. Don't do a crazy > symlink into a non-device-attribute portion of the sysfs tree, by doing > that you break all userspace tools and stuff like libudev will never > even see these attributes.
I guess I can fill in some info here about the use case needed: userspace tools (in this case, a tool called "crossystem") needs to look up a CBMEM entry by ID and read it. So, being able to find a fixed path like /sys/firmware/cbmem/<id>/mem is significantly easier than scanning all /sys/bus/coreboot/devices/coreboot*/id to find the right device first.
What exactly do we break here by adding symlinks? udev won't look into /sys/firmware, right?
Or, is there another good alternative that we could use to find a CBMEM entry by its id without needing to scan thru all coreboot bus type devices? Setting the device name to something more predictable (e.g., "cbmem-<id>") would require the coreboot bus type to "look ahead" and notice it's a CBMEM entry before registering the device, which wouldn't exactly be all that clean.
> > +What: /sys/firmware/cbmem/ > > +Date: August 2022 > > +Contact: Jack Rosenthal <jrosenth@chromium.org> > > +Description: > > + Coreboot provides a variety of data structures in CBMEM. This > > + directory contains each CBMEM entry, which can be found via > > + Coreboot tables. > > What happened to the coreboot name?
I removed it as it seemed like from your last message you didn't want it?
> Why cbmem? What is CBMEM?
I can add this to the next patch once I get clarifications on the above.
> Also, I asked before, but some note about "exposing all of these bios > values to userspace is not a security issue at all" would be nice, if > only to point at in a few years and say "wow we were naive"...
Right, I'll add this too.
Thanks,
Jack
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