Commit 995b3017 authored by Gerd Hoffmann's avatar Gerd Hoffmann
Browse files

hw/display: add ramfb, a simple boot framebuffer living in guest ram 



The boot framebuffer is expected to be configured by the firmware, so it
uses fw_cfg as interface.  Initialization goes as follows:

  (1) Check whenever etc/ramfb is present.
  (2) Allocate framebuffer from RAM.
  (3) Fill struct RAMFBCfg, write it to etc/ramfb.

Done.  You can write stuff to the framebuffer now, and it should appear
automagically on the screen.

Note that this isn't very efficient because it does a full display
update on each refresh.  No dirty tracking.  Dirty tracking would have
to be active for the whole ram slot, so that wouldn't be very efficient
either.  For a boot display which is active for a short time only this
isn't a big deal.  As permanent guest display something better should be
used (if possible).

This is the ramfb core code.  Some windup is needed for display devices
which want have a ramfb boot display.

Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Tested-by: default avatarLaszlo Ersek <lersek@redhat.com>
Message-id: 20180613122948.18149-2-kraxel@redhat.com
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 47479c55

hw/display/Makefile.objs

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common-obj-y += ramfb.o



common-obj-$(CONFIG_ADS7846) += ads7846.o

common-obj-$(CONFIG_VGA_CIRRUS) += cirrus_vga.o

common-obj-$(CONFIG_G364FB) += g364fb.o

hw/display/ramfb.c

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/*

 * early boot framebuffer in guest ram

 * configured using fw_cfg

 *

 * Copyright Red Hat, Inc. 2017

 *

 * Author:

 *     Gerd Hoffmann <kraxel@redhat.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2 or later.

 * See the COPYING file in the top-level directory.

 */

#include "qemu/osdep.h"

#include "qapi/error.h"

#include "hw/loader.h"

#include "hw/display/ramfb.h"

#include "ui/console.h"

#include "sysemu/sysemu.h"



struct QEMU_PACKED RAMFBCfg {

    uint64_t addr;

    uint32_t fourcc;

    uint32_t flags;

    uint32_t width;

    uint32_t height;

    uint32_t stride;

};



struct RAMFBState {

    DisplaySurface *ds;

    uint32_t width, height;

    struct RAMFBCfg cfg;

};



static void ramfb_fw_cfg_write(void *dev, off_t offset, size_t len)

{

    RAMFBState *s = dev;

    void *framebuffer;

    uint32_t stride, fourcc, format;

    hwaddr addr, length;



    s->width  = be32_to_cpu(s->cfg.width);

    s->height = be32_to_cpu(s->cfg.height);

    stride    = be32_to_cpu(s->cfg.stride);

    fourcc    = be32_to_cpu(s->cfg.fourcc);

    addr      = be64_to_cpu(s->cfg.addr);

    length    = stride * s->height;

    format    = qemu_drm_format_to_pixman(fourcc);



    fprintf(stderr, "%s: %dx%d @ 0x%" PRIx64 "\n", __func__,

            s->width, s->height, addr);

    framebuffer = address_space_map(&address_space_memory,

                                    addr, &length, false,

                                    MEMTXATTRS_UNSPECIFIED);

    if (!framebuffer || length < stride * s->height) {

        s->width = 0;

        s->height = 0;

        return;

    }

    s->ds = qemu_create_displaysurface_from(s->width, s->height,

                                            format, stride, framebuffer);

}



void ramfb_display_update(QemuConsole *con, RAMFBState *s)

{

    if (!s->width || !s->height) {

        return;

    }



    if (s->ds) {

        dpy_gfx_replace_surface(con, s->ds);

        s->ds = NULL;

    }



    /* simple full screen update */

    dpy_gfx_update_full(con);

}



RAMFBState *ramfb_setup(Error **errp)

{

    FWCfgState *fw_cfg = fw_cfg_find();

    RAMFBState *s;



    if (!fw_cfg || !fw_cfg->dma_enabled) {

        error_setg(errp, "ramfb device requires fw_cfg with DMA");

        return NULL;

    }



    s = g_new0(RAMFBState, 1);



    fw_cfg_add_file_callback(fw_cfg, "etc/ramfb",

                             NULL, ramfb_fw_cfg_write, s,

                             &s->cfg, sizeof(s->cfg), false);

    return s;

}

include/hw/display/ramfb.h

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#ifndef RAMFB_H

#define RAMFB_H



/* ramfb.c */

typedef struct RAMFBState RAMFBState;

void ramfb_display_update(QemuConsole *con, RAMFBState *s);

RAMFBState *ramfb_setup(Error **errp);



#endif /* RAMFB_H */