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    Subject[PATCH 3.16 055/328] fb: fix lost console when the user unplugs a USB adapter
    3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Mikulas Patocka <mpatocka@redhat.com>

    commit 8c5b044299951acd91e830a688dd920477ea1eda upstream.

    I have a USB display adapter using the udlfb driver and I use it on an ARM
    board that doesn't have any graphics card. When I plug the adapter in, the
    console is properly displayed, however when I unplug and re-plug the
    adapter, the console is not displayed and I can't access it until I reboot
    the board.

    The reason is this:
    When the adapter is unplugged, dlfb_usb_disconnect calls
    unlink_framebuffer, then it waits until the reference count drops to zero
    and then it deallocates the framebuffer. However, the console that is
    attached to the framebuffer device keeps the reference count non-zero, so
    the framebuffer device is never destroyed. When the USB adapter is plugged
    again, it creates a new device /dev/fb1 and the console is not attached to
    it.

    This patch fixes the bug by unbinding the console from unlink_framebuffer.
    The code to unbind the console is moved from do_unregister_framebuffer to
    a function unbind_console. When the console is unbound, the reference
    count drops to zero and the udlfb driver frees the framebuffer. When the
    adapter is plugged back, a new framebuffer is created and the console is
    attached to it.

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Cc: Dave Airlie <airlied@redhat.com>
    Cc: Bernie Thompson <bernie@plugable.com>
    Cc: Ladislav Michl <ladis@linux-mips.org>
    [b.zolnierkie: preserve old behavior for do_unregister_framebuffer()]
    Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/video/fbdev/core/fbmem.c | 38 +++++++++++++++++++++++++++-----
    1 file changed, 32 insertions(+), 6 deletions(-)

    --- a/drivers/video/fbdev/core/fbmem.c
    +++ b/drivers/video/fbdev/core/fbmem.c
    @@ -1687,12 +1687,12 @@ static int do_register_framebuffer(struc
    return 0;
    }

    -static int do_unregister_framebuffer(struct fb_info *fb_info)
    +static int unbind_console(struct fb_info *fb_info)
    {
    struct fb_event event;
    - int i, ret = 0;
    + int ret;
    + int i = fb_info->node;

    - i = fb_info->node;
    if (i < 0 || i >= FB_MAX || registered_fb[i] != fb_info)
    return -EINVAL;

    @@ -1707,17 +1707,29 @@ static int do_unregister_framebuffer(str
    unlock_fb_info(fb_info);
    console_unlock();

    + return ret;
    +}
    +
    +static int __unlink_framebuffer(struct fb_info *fb_info);
    +
    +static int do_unregister_framebuffer(struct fb_info *fb_info)
    +{
    + struct fb_event event;
    + int ret;
    +
    + ret = unbind_console(fb_info);
    +
    if (ret)
    return -EINVAL;

    pm_vt_switch_unregister(fb_info->dev);

    - unlink_framebuffer(fb_info);
    + __unlink_framebuffer(fb_info);
    if (fb_info->pixmap.addr &&
    (fb_info->pixmap.flags & FB_PIXMAP_DEFAULT))
    kfree(fb_info->pixmap.addr);
    fb_destroy_modelist(&fb_info->modelist);
    - registered_fb[i] = NULL;
    + registered_fb[fb_info->node] = NULL;
    num_registered_fb--;
    fb_cleanup_device(fb_info);
    event.info = fb_info;
    @@ -1730,7 +1742,7 @@ static int do_unregister_framebuffer(str
    return 0;
    }

    -int unlink_framebuffer(struct fb_info *fb_info)
    +static int __unlink_framebuffer(struct fb_info *fb_info)
    {
    int i;

    @@ -1742,6 +1754,20 @@ int unlink_framebuffer(struct fb_info *f
    device_destroy(fb_class, MKDEV(FB_MAJOR, i));
    fb_info->dev = NULL;
    }
    +
    + return 0;
    +}
    +
    +int unlink_framebuffer(struct fb_info *fb_info)
    +{
    + int ret;
    +
    + ret = __unlink_framebuffer(fb_info);
    + if (ret)
    + return ret;
    +
    + unbind_console(fb_info);
    +
    return 0;
    }
    EXPORT_SYMBOL(unlink_framebuffer);
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