Hi Jaya,

On Wed, 30 Jun 2010 09:52:13 Jaya Kumar wrote:

On Tue, Jun 29, 2010 at 4:29 AM, Bruno Prémont
[off-list ref] wrote:

quoted

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.

Well I talk about fbcon as that's the trigger I have seen causing an
issue.

I'm fine with rewriting the changelog as to just talk about the
correct/expected order of initialization.

Thanks for looking at it,
Bruno

What I see is that you originally had in picolcd:

quoted

       error = register_framebuffer(info);

...

quoted

       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

quoted

Note: this BUG() deadlocks ttys.

Signed-off-by: Bruno Prémont <bonbons@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