Messages in this thread | | | Date | Sun, 31 Dec 2006 15:12:26 +0100 (MET) | From | Jan Engelhardt <> | Subject | Re: [PATCH] Open Firmware device tree virtual filesystem |
| |
On Dec 30 2006 15:38, Mitch Bradley wrote: > > Request for comments. > > It is similar in some respect to fs/proc/proc_devtree.c , but does > not use procfs, nor does it require an intermediate layer of code > to create a flattened representation of the device tree.
NB: openpromfs does not use procfs either. It just happens to be mounted somewhere down there.
> +++ b/Documentation/filesystems/ofwfs.txt > +== Property Value Encoding == > + > +A regular file in ofwfs contains the exact byte sequence that > +comprises the OFW property value. Properties are not reformatted > +into text form, so numeric property values appear as binary > +integers. While this is inconvenient for viewing, it is generally > +easier for programs that read property values, and it means that > +Open Firmware documentation about property values applies > +directly, without having to separately document an ASCII > +transformation (which would have to separately specified for > +different kinds of properties).
I appreciate the ASCII formatting that openpromfs currently does. Perhaps, should OFWFS be used, it could offer both?
> +== Environment Assumptions == > + > +The ofwfs code assumes that the Open Firmware client interface > +callback can be executed during Linux kernel startup > +(specifically, at "core_initcall" time). When ofwfs is > +initialized, it copies out the property values, so that subsequent > +accesses to the tree do not require callbacks into OFW.
openpromfs also has many parts read-only, only one object, /options/security-password, is writable. Hence caching it once and forever seems ok.
BUT, the eeprom utility may be used to modify values, and if used, I would like to see ofwfs show the updated value. openpromfs does it today:
15:09 ares:/proc/openprom/options # cat oem-banner? false 15:09 ares:/proc/openprom/options # eeprom 'oem-banner?=true' 15:09 ares:/proc/openprom/options # cat oem-banner? true
(BTW, why does not openpromfs have it rw?)
> +== Recommended Mount Point == > + > +The recommended mount point for ofwfs is /ofw. (TBD: Should it be > +mounted somewhere under /sys instead?)
Somewhere in /sys/firmware perhaps.
-`J' -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |