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.
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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