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From: Jaya Kumar on 29 Jun 2010 22:00
On Tue, Jun 29, 2010 at 4:29 AM, Bruno Pr�mont
<bonbons(a)linux-vserver.org> wrote:
> We need to call fb_deferred_io_init() before we register_framebuffer()
> as otherwise, in case fbcon uses our framebuffer, we will get a BUG()
> because in picolcd_fb_imageblit() we schedule defio which has not
> been initialized yet.

Hi Bruno,

The comment above seems confusing to me in that it talks about fbcon
and defio schedule.

What I see is that you originally had in picolcd:

> error = register_framebuffer(info);
....
> fb_deferred_io_init(info);

which was a bug because it called register_framebuffer (ie: made the
framebuffer available for use) and only then initialized the defio
handlers which were needed for that framebuffer memory to be used.
Drivers must always call defio_init _before_ register_framebuffer. The
bug fix to picolcd below looks correct because it now does that
sequence in the correct order.

Thanks,
jaya



>
> Note: this BUG() deadlocks ttys.
>
> Signed-off-by: Bruno Pr�mont <bonbons(a)linux-vserver.org>
> ---
> �drivers/hid/hid-picolcd.c | � �4 ++--
> �1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hid/hid-picolcd.c b/drivers/hid/hid-picolcd.c
> index 95253b3..883d720 100644
> --- a/drivers/hid/hid-picolcd.c
> +++ b/drivers/hid/hid-picolcd.c
> @@ -707,18 +707,19 @@ static int picolcd_init_framebuffer(struct picolcd_data *data)
> � � � � � � � �dev_err(dev, "failed to create sysfs attributes\n");
> � � � � � � � �goto err_cleanup;
> � � � �}
> + � � � fb_deferred_io_init(info);
> � � � �data->fb_info � �= info;
> � � � �error = register_framebuffer(info);
> � � � �if (error) {
> � � � � � � � �dev_err(dev, "failed to register framebuffer\n");
> � � � � � � � �goto err_sysfs;
> � � � �}
> - � � � fb_deferred_io_init(info);
> � � � �/* schedule first output of framebuffer */
> � � � �schedule_delayed_work(&info->deferred_work, 0);
> � � � �return 0;
>
> �err_sysfs:
> + � � � fb_deferred_io_cleanup(info);
> � � � �device_remove_file(dev, &dev_attr_fb_update_rate);
> �err_cleanup:
> � � � �data->fb_vbitmap = NULL;
> @@ -747,7 +748,6 @@ static void picolcd_exit_framebuffer(struct picolcd_data *data)
> � � � �data->fb_bpp � � = 0;
> � � � �data->fb_info � �= NULL;
> � � � �device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);
> - � � � fb_deferred_io_cleanup(info);
> � � � �unregister_framebuffer(info);
> � � � �vfree(fb_bitmap);
> � � � �kfree(fb_vbitmap);
> --
> 1.7.1
>
>
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Prev: Add a pair of system calls to make extended file stats available [ver #2]
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