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x86 discoverability is over ratedx86 discoverability is over ratedPosted Aug 29, 2011 0:28 UTC (Mon) by mjg59 (subscriber, #23239)In reply to: x86 discoverability is over rated by giraffedata Parent article: The udev tail wags the dog
Device tree and ACPI are both mechanisms for permitting discovery of non-discoverable devices. Device tree also provides metadata such as GPIO mappings, while ACPI abstracts that.
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x86 discoverability is over rated Posted Aug 29, 2011 1:39 UTC (Mon) by dlang (✭ supporter ✭, #313) [Link]
ACPI is a way for the kernel to lookup what hardware exists in tables created by the hardware manufacturer. The tables are (in theory) OS independant.
Device Trees are a way for the System Administrator who installs an OS on the system what hardware exists.
It's far more likely that the hardware manufacturer is going to accurately identify what hardware exists than it is that the System Administrator is going to know what hardware exists on a system.
Device Trees may look like they are discoverable if you are only looking at it from the point of view of an OS that has the Device Tree provided to it. But from the point of view of the person trying to install the system who has to figure out what to put in the Device Tree, they are not discoverable, they are the output of research, not the source of information.
x86 discoverability is over rated Posted Aug 29, 2011 2:15 UTC (Mon) by mjg59 (subscriber, #23239) [Link]
The device tree is supposed to be provided by the boot loader, which in a typical ARM environment is supplied by the system vendor.
x86 discoverability is over rated Posted Aug 29, 2011 2:26 UTC (Mon) by dlang (✭ supporter ✭, #313) [Link]
in a typical ARM environment the entire OS is provided by the system vendor, that's not a very good argument.
ARM vendors don't really care about Device Trees, they are pretty happy just hard-coding the kernel itself.
it's the people who want to upgrade the devices and people who want to maintain the upstream tree that want the consolidation made available by device trees.
x86 discoverability is over rated Posted Oct 18, 2011 16:15 UTC (Tue) by jcm (subscriber, #18262) [Link]
ARM vendors may care about enumerable device information if they are targeting general purpose Operating Systems as opposed to the existing tight vertical integration process.
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