linux-kernel - Re: [PATCH 0/6] Apple device properties

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Date:	Thu, 4 Aug 2016 15:57:10 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Lukas Wunner <lukas@...ner.de>
Cc:	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andreas Noever <andreas.noever@...il.com>,
	Pierre Moreau <pierre.morrow@...e.fr>, reverser@....as,
	grub-devel@....org, x86@...nel.org,
	Aleksey Makarov <aleksey.makarov@...aro.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 0/6] Apple device properties

On Thu, 28 Jul, at 02:25:41AM, Lukas Wunner wrote:
> Apple EFI drivers supply device properties which are needed to support
> Macs optimally.
> 
> This series extends the efistub to retrieve the device properties before
> ExitBootServices is called (patch [1/6]). They are assigned to devices
> in an fs_initcall (patch [5/6]). As a first use case, the Thunderbolt
> driver is amended to take advantage of the Device ROM supplied by EFI
> (patch [6/6]).
> 
> A by-product is a parser for EFI Device Paths which finds the struct
> device corresponding to a given path. This is needed to assign
> properties to their devices (patch [3/6]).
> 
> 
> I've pushed these patches to GitHub where they can be reviewed more
> comfortably with green/red highlighting:
> https://github.com/l1k/linux/commits/apple_properties_v1
> 
> 
> It would be good if one of the resident EFI experts could look over
> patch [1/6] to see if I've made any mistakes that might prevent this
> from working on 32 bit. It was only tested on 64 bit, I don't know
> anyone with an older Mac who could test this.
> 
> Specifically, is the following okay:
> efi_early->call((unsigned long)sys_table->boottime->locate_protocol, ...)

This probably isn't going to work with EFI mixed mode because you
can't jump through pointers at runtime - that's the whole point of the
setup_boot_services*bits() code.

> It would be convenient to have LocateProtocol or LocateHandleBuffer in
> struct efi_config so that they can be called with efi_call_early().
> Would a patch to add those be entertained? Right now we only offer
> LocateHandle and HandleProtocol, which is somewhat cumbersome and
> needs more code as the setup_pci() functions show.

Yes, go for it. Doing this would make it work with EFI mixed mode too.