On 23.07.2013, at 23:55, Scott Wood wrote: > On 07/23/2013 04:44:02 PM, Alexander Graf wrote: >> Am 23.07.2013 um 23:19 schrieb Scott Wood <scottw...@freescale.com>: >> > On 07/23/2013 04:15:59 PM, Alexander Graf wrote: >> >> On 23.07.2013, at 21:38, Scott Wood wrote: >> >> > On 07/22/2013 10:28:17 AM, Alexander Graf wrote: >> >> >> Today we generate the device tree once on machine initialization and >> >> >> then >> >> >> store the finalized blob in memory to reload it on reset. >> >> >> This is bad for 2 reasons. First we potentially waste a bunch of RAM >> >> >> for no >> >> >> good reason, as we have all information required to regenerate the >> >> >> device >> >> >> tree available anyways. >> >> >> The second reason is even more important. On machine init when we >> >> >> generate >> >> >> the device tree for the first time, we don't have all of the devices >> >> >> fully >> >> >> initialized yet. But the device tree needs to potentially walk devices >> >> >> to >> >> >> put information about them into the device tree. >> >> > >> >> > If you can't produce the entire device tree at init time, how can you >> >> > calculate its size with a dry run? >> >> > >> >> > Device trees are generally pretty small; couldn't we just set a maximum >> >> > size and allocate that much space? >> >> It's what we do, unless we load it from the disk. In that case we take >> >> the fdt size from disk. >> > >> > So why do we need the dry run stuff? >> Because dumpdtb otherwise generates a halfway complete dtb on the first dry >> pass as device realization is yet incomplete :). > > What I mean is why have a first pass at all?
Ah, you mean we should just always limit ourselves to the 8MB we reserve for the device tree? That would work, yes. Alex
