linux-kernel - Re: [PATCH v2 10/10] x86, efi: EFI boot stub support

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Message-ID: <1315922476.3466.60.camel@mfleming-mobl1.ger.corp.intel.com>
Date:	Tue, 13 Sep 2011 15:01:16 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...ux.intel.com>, x86@...nel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Waychison <mikew@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Maarten Lankhorst <m.b.lankhorst@...il.com>
Subject: Re: [PATCH v2 10/10] x86, efi: EFI boot stub support

On Tue, 2011-09-13 at 14:29 +0100, Matthew Garrett wrote:
> On Mon, Sep 12, 2011 at 03:34:54PM +0100, Matt Fleming wrote:
> 
> > +	status = efi_call_phys5(sys_table->boottime->locate_handle,
> > +				EFI_LOCATE_BY_PROTOCOL, proto,
> > +				NULL, &size, gop_handle);
> > +	if (status != EFI_SUCCESS)
> > +		goto free_handle;
> > +
> > +	nr_gops = size / sizeof(void *);
> > +	for (i = 0; i < nr_gops; i++) {
> > +		void *h = gop_handle[i];
> > +
> > +		status = efi_call_phys3(sys_table->boottime->handle_protocol,
> > +					h, proto, &gop);
> > +		if (status != EFI_SUCCESS)
> > +			continue;
> > +
> > +		status = efi_call_phys4(gop->query_mode, gop, gop->mode->mode,
> > +					&size, &info);
> > +		if (status == EFI_SUCCESS)
> > +			break;
> > +	}
> 
> Apple do something funky here, which is to provide a GOP that's not 
> backed by real hardware but which muxes writes out to multiple outputs 
> in order to handle the multiple display case without screwing up aspect 
> ratio. That's fine, except that the stride reported for the fake one is 
> just the horizontal width of the logical display. That results in things 
> failing badly. The real one also implements PCIIO. My workaround so far 
> has been to look for a GOP that handles PCIIO and use it if found, and 
> otherwise just fall back to the first GOP.

Ah right, thanks for that. I actually implement that strategy when
searching for a UGA (checking for PCIIO) but without falling back to the
first one if no PCIIO protocol is found. Your proposed scheme seems much
more robust so I'll respin this patch.

-- 
Matt Fleming, Intel Open Source Technology Center

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