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: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 20180613122948.18149-2-kraxel@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Gerd Hoffmann 2018-06-13 14:29:45 +02:00
parent 47479c55b0
commit 995b30179b
3 changed files with 106 additions and 0 deletions

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@ -1,3 +1,5 @@
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

95
hw/display/ramfb.c Normal file
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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;
}

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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 */