Hi Heiko,
sorry for the long delay.
On 12/31/2011 10:45 AM, Heiko Stübner wrote:
> With this optional callback the driver is notified when the first page
> is entered into the pagelist and a new deferred_io call is scheduled.
>
> A possible use-case for this is runtime-pm. In the first_io call
> pm_runtime_get()
> could be called, which starts an asynchronous runtime_resume of the
> device. In the deferred_io callback a call to
> pm_runtime_barrier()
> makes the sure, the device is resumed by then and a
> pm_runtime_put()
> may put the device back to sleep.
>
> Also, some SoCs may use the runtime-pm system to determine if they
> are able to enter deeper idle states. Therefore it is necessary to
> keep the use-count from the first written page until the conclusion
> of the screen update, to prevent the system from going to sleep before
> completing the pending update.
>
> Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
while I consider this patch acceptable, I don't see any reason to apply it as
long as there is no driver actually using it.
Best regards,
Florian Tobias Schandinat
> ---
> drivers/video/fb_defio.c | 4 ++++
> include/linux/fb.h | 1 +
> 2 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
> index c27e153..070f26f 100644
> --- a/drivers/video/fb_defio.c
> +++ b/drivers/video/fb_defio.c
> @@ -107,6 +107,10 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
> /* protect against the workqueue changing the page list */
> mutex_lock(&fbdefio->lock);
>
> + /* first write in this cycle, notify the driver */
> + if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
> + fbdefio->first_io(info);
> +
> /*
> * We want the page to remain locked from ->page_mkwrite until
> * the PTE is marked dirty to avoid page_mkclean() being called
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 1d6836c..b86cd41 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -602,6 +602,7 @@ struct fb_deferred_io {
> struct mutex lock; /* mutex that protects the page list */
> struct list_head pagelist; /* list of touched pages */
> /* callback */
> + void (*first_io)(struct fb_info *info);
> void (*deferred_io)(struct fb_info *info, struct list_head *pagelist);
> };
> #endif
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