Hi Jaya,
On Wed, 30 Jun 2010 09:52:13 Jaya Kumar wrote:
> On Tue, Jun 29, 2010 at 4:29 AM, Bruno Prémont
> <bonbons@xxxxxxxxxxxxxxxxx> 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.
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:
>
> > 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 Prémont <bonbons@xxxxxxxxxxxxxxxxx>
> > ---
> > 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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