Message-ID: <CANq1E4TtF+jdLQqH_xtVse3cBwahMDaP41K_C2ZtPWLKe6D6Bg@mail.gmail.com>
Date:	Wed, 17 Jul 2013 19:40:51 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	David Airlie <airlied@...ux.ie>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	David Herrmann <dh.herrmann@...il.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 03/14] x86: provide platform-devices for boot-framebuffers

Hi

Any comments on this?

On Thu, Jul 4, 2013 at 2:25 PM, David Herrmann <dh.herrmann@...il.com> wrote:
> 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@...il.com>
> ---
>  arch/x86/Kconfig                 | 26 +++++++++++
>  arch/x86/include/asm/sysfb.h     | 41 +++++++++++++++++
>  arch/x86/kernel/Makefile         |  2 +
>  arch/x86/kernel/sysfb.c          | 71 ++++++++++++++++++++++++++++++
>  arch/x86/kernel/sysfb_simplefb.c | 95 ++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 235 insertions(+)
>  create mode 100644 arch/x86/include/asm/sysfb.h
>  create mode 100644 arch/x86/kernel/sysfb.c
>  create mode 100644 arch/x86/kernel/sysfb_simplefb.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index fe120da..54a93a5 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2255,6 +2255,32 @@ config RAPIDIO
>
>  source "drivers/rapidio/Kconfig"
>
> +config X86_SYSFB
> +       bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
> +       help
> +         Firmwares often provide initial graphics framebuffers so the BIOS,
> +         bootloader or kernel can show basic video-output during boot for
> +         user-guidance and debugging. Historically, x86 used the VESA BIOS
> +         Extensions and EFI-framebuffers for this, which are mostly limited
> +         to x86.
> +         This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
> +         framebuffers so the new generic system-framebuffer drivers can be
> +         used on x86. If the framebuffer is not compatible with the generic
> +         modes, it is adverticed as fallback platform framebuffer so legacy
> +         drivers like efifb, vesafb and uvesafb can pick it up.
> +         If this option is not selected, all system framebuffers are always
> +         marked as fallback platform framebuffers as usual.
> +
> +         Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
> +         not be able to pick up generic system framebuffers if this option
> +         is selected. You are highly encouraged to enable simplefb as
> +         replacement if you select this option. simplefb can correctly deal
> +         with generic system framebuffers. But you should still keep vesafb
> +         and others enabled as fallback if a system framebuffer is
> +         incompatible with simplefb.
> +
> +         If unsure, say Y.
> +
>  endmenu
>
>
> diff --git a/arch/x86/include/asm/sysfb.h b/arch/x86/include/asm/sysfb.h
> new file mode 100644
> index 0000000..2395fe0
> --- /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@...il.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 */
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 7bd3bd3..c5e7677 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -100,6 +100,8 @@ obj-$(CONFIG_X86_CHECK_BIOS_CORRUPTION) += check.o
>  obj-$(CONFIG_SWIOTLB)                  += pci-swiotlb.o
>  obj-$(CONFIG_OF)                       += devicetree.o
>  obj-$(CONFIG_UPROBES)                  += uprobes.o
> +obj-y                                  += sysfb.o
> +obj-$(CONFIG_X86_SYSFB)                        += sysfb_simplefb.o
>
>  obj-$(CONFIG_PERF_EVENTS)              += perf_regs.o
>
> diff --git a/arch/x86/kernel/sysfb.c b/arch/x86/kernel/sysfb.c
> new file mode 100644
> index 0000000..7f30e19
> --- /dev/null
> +++ b/arch/x86/kernel/sysfb.c
> @@ -0,0 +1,71 @@
> +/*
> + * Generic System Framebuffers on x86
> + * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@...il.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.
> + */
> +
> +/*
> + * Simple-Framebuffer support for x86 systems
> + * Create a platform-device for any available boot framebuffer. The
> + * simple-framebuffer platform device is already available on DT systems, so
> + * this module parses the global "screen_info" object and creates a suitable
> + * platform device compatible with the "simple-framebuffer" DT object. If
> + * the framebuffer is incompatible, we instead create a legacy
> + * "vesa-framebuffer", "efi-framebuffer" or "platform-framebuffer" device and
> + * pass the screen_info as platform_data. This allows legacy drivers
> + * to pick these devices up without messing with simple-framebuffer drivers.
> + * The global "screen_info" is still valid at all times.
> + *
> + * If CONFIG_X86_SYSFB is not selected, we never register "simple-framebuffer"
> + * platform devices, but only use legacy framebuffer devices for
> + * backwards compatibility.
> + *
> + * TODO: We set the dev_id field of all platform-devices to 0. This allows
> + * other x86 OF/DT parsers to create such devices, too. However, they must
> + * start at offset 1 for this to work.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/platform_data/simplefb.h>
> +#include <linux/platform_device.h>
> +#include <linux/screen_info.h>
> +#include <asm/sysfb.h>
> +
> +static __init int sysfb_init(void)
> +{
> +       struct screen_info *si = &screen_info;
> +       struct simplefb_platform_data mode;
> +       struct platform_device *pd;
> +       const char *name;
> +       bool compatible;
> +       int ret;
> +
> +       /* try to create a simple-framebuffer device */
> +       compatible = parse_mode(si, &mode);
> +       if (compatible) {
> +               ret = create_simplefb(si, &mode);
> +               if (!ret)
> +                       return 0;
> +       }
> +
> +       /* if the FB is incompatible, create a legacy framebuffer device */
> +       if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
> +               name = "efi-framebuffer";
> +       else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
> +               name = "vesa-framebuffer";
> +       else
> +               name = "platform-framebuffer";
> +
> +       pd = platform_device_register_resndata(NULL, name, 0,
> +                                              NULL, 0, si, sizeof(*si));
> +       return IS_ERR(pd) ? PTR_ERR(pd) : 0;
> +}
> +
> +device_initcall(sysfb_init);
> diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
> new file mode 100644
> index 0000000..22513e9
> --- /dev/null
> +++ b/arch/x86/kernel/sysfb_simplefb.c
> @@ -0,0 +1,95 @@
> +/*
> + * Generic System Framebuffers on x86
> + * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@...il.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.
> + */
> +
> +/*
> + * simple-framebuffer probing
> + * Try to convert "screen_info" into a "simple-framebuffer" compatible mode.
> + * If the mode is incompatible, we return "false" and let the caller create
> + * legacy nodes instead.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/platform_data/simplefb.h>
> +#include <linux/platform_device.h>
> +#include <linux/screen_info.h>
> +#include <asm/sysfb.h>
> +
> +static const char simplefb_resname[] = "BOOTFB";
> +static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;
> +
> +/* try parsing x86 screen_info into a simple-framebuffer mode struct */
> +__init bool parse_mode(const struct screen_info *si,
> +                      struct simplefb_platform_data *mode)
> +{
> +       const struct simplefb_format *f;
> +       __u8 type;
> +       unsigned int i;
> +
> +       type = si->orig_video_isVGA;
> +       if (type != VIDEO_TYPE_VLFB && type != VIDEO_TYPE_EFI)
> +               return false;
> +
> +       for (i = 0; i < ARRAY_SIZE(formats); ++i) {
> +               f = &formats[i];
> +               if (si->lfb_depth == f->bits_per_pixel &&
> +                   si->red_size == f->red.length &&
> +                   si->red_pos == f->red.offset &&
> +                   si->green_size == f->green.length &&
> +                   si->green_pos == f->green.offset &&
> +                   si->blue_size == f->blue.length &&
> +                   si->blue_pos == f->blue.offset &&
> +                   si->rsvd_size == f->transp.length &&
> +                   si->rsvd_pos == f->transp.offset) {
> +                       mode->format = f->name;
> +                       mode->width = si->lfb_width;
> +                       mode->height = si->lfb_height;
> +                       mode->stride = si->lfb_linelength;
> +                       return true;
> +               }
> +       }
> +
> +       return false;
> +}
> +
> +__init int create_simplefb(const struct screen_info *si,
> +                          const struct simplefb_platform_data *mode)
> +{
> +       struct platform_device *pd;
> +       struct resource res;
> +       unsigned long len;
> +
> +       /* don't use lfb_size as it may contain the whole VMEM instead of only
> +        * the part that is occupied by the framebuffer */
> +       len = mode->height * mode->stride;
> +       len = PAGE_ALIGN(len);
> +       if (len > si->lfb_size << 16) {
> +               printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
> +               return -EINVAL;
> +       }
> +
> +       /* setup IORESOURCE_MEM as framebuffer memory */
> +       memset(&res, 0, sizeof(res));
> +       res.flags = IORESOURCE_MEM;
> +       res.name = simplefb_resname;
> +       res.start = si->lfb_base;
> +       res.end = si->lfb_base + len - 1;
> +       if (res.end <= res.start)
> +               return -EINVAL;
> +
> +       pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
> +                                              &res, 1, mode, sizeof(*mode));
> +       if (IS_ERR(pd))
> +               return PTR_ERR(pd);
> +
> +       return 0;
> +}
> --
> 1.8.3.2
>
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