On Tue 08 May 09:10 PDT 2018, Luis R. Rodriguez wrote: > On Tue, May 08, 2018 at 03:38:05PM +0000, Luis R. Rodriguez wrote: > > On Fri, May 04, 2018 at 12:44:37PM -0700, Martijn Coenen wrote: > > > On Wed, Apr 25, 2018 at 10:55 AM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote: [..] > > > 2) Most of those paths are not mounted by the time the corresponding > > > drivers are loaded, because pretty much all Android kernels today are > > > built without module support, and therefore drivers are loaded well > > > before the firmware partition is mounted > > I've given this some more thought and you can address this with initramfs, > this is how other Linux distributions are addressing this. One way to > address this automatically is to scrape the drivers built-in or needed early on > boot in initamfs and if the driver has a MODULE_FIRMWARE() its respective > firmware is added to initramfs as well. > That could be done, but it would not change the fact that the /sys/class/firmware is ABI and you may not break it. And it doesn't change the fact that the ramdisk would have to be over 100mb to facilitate this. > If you *don't* use initramfs, then yes you can obviously run into issues > where your firmware may not be accessible if the driver is somehow loaded > early. > This is still a problem that lacks a solution. > > > 3) I think we use _FALLBACK because doing this with uevents is just > > > the easiest thing to do; our init code has a firmware helper that > > > deals with this and searches the paths that we care about > > > > > > 2) will change at some point, because Android is moving towards a > > > model where device-specific peripheral drivers will be loaded as > > > modules, and since those modules would likely come from the same > > > partition as the firmware, it's possible that the direct load would > > > succeed (depending on whether the custom path is configured there or > > > not). But I don't think we can rely on the direct loader even in those > > > cases, unless we could configure it with multiple custom paths. > > Using initramfs will help, but because of the custom path needs -- you're > right, we don't have anything for that yet, its also a bit unclear if > something nice and clean can be drawn up for it. So perhaps dealing with > the fallback mechanism is the way to go for this for sure, since we already > have support for it. > > Just keep in mind that the fallback mechanism costs you about ~13436 bytes. > Remember that putting the firmware in the ramdisk would cost about 10000x (yes, ten thousand times) more ram. > So, if someone comes up with a clean interface for custom paths I'd love > to consider it to avoid those 13436 bytes. > Combined with a way of synchronizing this with the availability of the firmware, this would be a nice thing! Regards, Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
