x86: provide platform-devices for boot-framebuffers

The current situation regarding boot-framebuffers (VGA, VESA/VBE, EFI) on
x86 causes troubles when loading multiple fbdev drivers. The global
"struct screen_info" does not provide any state-tracking about which
drivers use the FBs. request_mem_region() theoretically works, but
unfortunately vesafb/efifb ignore it due to quirks for broken boards.

Avoid this by creating a platform framebuffer devices with a pointer
to the "struct screen_info" as platform-data. Drivers can now create
platform-drivers and the driver-core will refuse multiple drivers being
active simultaneously.

We keep the screen_info available for backwards-compatibility. Drivers
can be converted in follow-up patches.

Different devices are created for VGA/VESA/EFI FBs to allow multiple
drivers to be loaded on distro kernels. We create:
 - "vesa-framebuffer" for VBE/VESA graphics FBs
 - "efi-framebuffer" for EFI FBs
 - "platform-framebuffer" for everything else
This allows to load vesafb, efifb and others simultaneously and each
picks up only the supported FB types.

Apart from platform-framebuffer devices, this also introduces a
compatibility option for "simple-framebuffer" drivers which recently got
introduced for OF based systems. If CONFIG_X86_SYSFB is selected, we
try to match the screen_info against a simple-framebuffer supported
format. If we succeed, we create a "simple-framebuffer" device instead
of a platform-framebuffer.
This allows to reuse the simplefb.c driver across architectures and also
to introduce a SimpleDRM driver. There is no need to have vesafb.c,
efifb.c, simplefb.c and more just to have architecture specific quirks
in their setup-routines.

Instead, we now move the architecture specific quirks into x86-setup and
provide a generic simple-framebuffer. For backwards-compatibility (if
strange formats are used), we still allow vesafb/efifb to be loaded
simultaneously and pick up all remaining devices.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Link: http://lkml.kernel.org/r/1375445127-15480-4-git-send-email-dh.herrmann@gmail.com
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/arch/x86/include/asm/sysfb.h b/arch/x86/include/asm/sysfb.h
new file mode 100644
index 0000000000000..2395fe03f56bc
--- /dev/null
+++ b/arch/x86/include/asm/sysfb.h
@@ -0,0 +1,41 @@
+#ifndef _ARCH_X86_KERNEL_SYSFB_H
+#define _ARCH_X86_KERNEL_SYSFB_H
+
+/*
+ * Generic System Framebuffers on x86
+ * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/platform_data/simplefb.h>
+#include <linux/screen_info.h>
+
+#ifdef CONFIG_X86_SYSFB
+
+bool parse_mode(const struct screen_info *si,
+		struct simplefb_platform_data *mode);
+int create_simplefb(const struct screen_info *si,
+		    const struct simplefb_platform_data *mode);
+
+#else /* CONFIG_X86_SYSFB */
+
+static inline bool parse_mode(const struct screen_info *si,
+			      struct simplefb_platform_data *mode)
+{
+	return false;
+}
+
+static inline int create_simplefb(const struct screen_info *si,
+				  const struct simplefb_platform_data *mode)
+{
+	return -EINVAL;
+}
+
+#endif /* CONFIG_X86_SYSFB */
+
+#endif /* _ARCH_X86_KERNEL_SYSFB_H */