It is possible that acpi_evaluate_integer might fail and value would not be
set to any value so correct this defect by returning 0 in case of an
error. This is also the correct thing to return because the backlight
subsystem will print the old value of brightness in this case.
Signed-off-by: Giedrius Statkevičius <[email protected]>
---
drivers/platform/x86/asus-laptop.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/platform/x86/asus-laptop.c b/drivers/platform/x86/asus-laptop.c
index 9a69734..15f1311 100644
--- a/drivers/platform/x86/asus-laptop.c
+++ b/drivers/platform/x86/asus-laptop.c
@@ -775,8 +775,10 @@ static int asus_read_brightness(struct backlight_device *bd)
rv = acpi_evaluate_integer(asus->handle, METHOD_BRIGHTNESS_GET,
NULL, &value);
- if (ACPI_FAILURE(rv))
+ if (ACPI_FAILURE(rv)) {
pr_warn("Error reading brightness\n");
+ return 0;
+ }
return value;
}
--
2.8.0
On Sat, Apr 16, 2016 at 3:27 AM, Giedrius Statkevičius
<[email protected]> wrote:
> It is possible that acpi_evaluate_integer might fail and value would not be
> set to any value so correct this defect by returning 0 in case of an
> error. This is also the correct thing to return because the backlight
> subsystem will print the old value of brightness in this case.
>
> Signed-off-by: Giedrius Statkevičius <[email protected]>
> ---
> drivers/platform/x86/asus-laptop.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/asus-laptop.c b/drivers/platform/x86/asus-laptop.c
> index 9a69734..15f1311 100644
> --- a/drivers/platform/x86/asus-laptop.c
> +++ b/drivers/platform/x86/asus-laptop.c
> @@ -775,8 +775,10 @@ static int asus_read_brightness(struct backlight_device *bd)
>
> rv = acpi_evaluate_integer(asus->handle, METHOD_BRIGHTNESS_GET,
> NULL, &value);
> - if (ACPI_FAILURE(rv))
> + if (ACPI_FAILURE(rv)) {
> pr_warn("Error reading brightness\n");
> + return 0;
> + }
This looks like a workaround.
I suppose the real fix is to return here an error code and fix all callers, like
drivers/video/backlight/backlight.c.
>
> return value;
> }
> --
> 2.8.0
>
--
With Best Regards,
Andy Shevchenko
On Fri, Apr 22, 2016 at 02:09:22AM +0300, Andy Shevchenko wrote:
> On Sat, Apr 16, 2016 at 3:27 AM, Giedrius Statkevičius
> <[email protected]> wrote:
> > It is possible that acpi_evaluate_integer might fail and value would not be
> > set to any value so correct this defect by returning 0 in case of an
> > error. This is also the correct thing to return because the backlight
> > subsystem will print the old value of brightness in this case.
> >
> > Signed-off-by: Giedrius Statkevičius <[email protected]>
> > ---
> > drivers/platform/x86/asus-laptop.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/asus-laptop.c b/drivers/platform/x86/asus-laptop.c
> > index 9a69734..15f1311 100644
> > --- a/drivers/platform/x86/asus-laptop.c
> > +++ b/drivers/platform/x86/asus-laptop.c
> > @@ -775,8 +775,10 @@ static int asus_read_brightness(struct backlight_device *bd)
> >
> > rv = acpi_evaluate_integer(asus->handle, METHOD_BRIGHTNESS_GET,
> > NULL, &value);
> > - if (ACPI_FAILURE(rv))
> > + if (ACPI_FAILURE(rv)) {
> > pr_warn("Error reading brightness\n");
> > + return 0;
> > + }
>
> This looks like a workaround.
> I suppose the real fix is to return here an error code and fix all callers, like
> drivers/video/backlight/backlight.c.
>
It just fixes the behaviour according to the current code in that file. I
suppose that would be nice but I don't think it would make any difference
because the backlight core code still prints out ->props.brightness in case
ops->get_brightness fails. Just the difference would be that now actual error
messages are printed in the drivers themselves instead of generic messages from
the backlight core. Anyway, I think the current behaviour is more useful because
the drivers know better about what has failed.
On Fri, Apr 22, 2016 at 10:43:30AM +0300, Giedrius Statkevičius wrote:
> On Fri, Apr 22, 2016 at 02:09:22AM +0300, Andy Shevchenko wrote:
> > On Sat, Apr 16, 2016 at 3:27 AM, Giedrius Statkevičius
> > <[email protected]> wrote:
> > > It is possible that acpi_evaluate_integer might fail and value would not be
> > > set to any value so correct this defect by returning 0 in case of an
> > > error. This is also the correct thing to return because the backlight
> > > subsystem will print the old value of brightness in this case.
> > >
> > > Signed-off-by: Giedrius Statkevičius <[email protected]>
> > > ---
> > > drivers/platform/x86/asus-laptop.c | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/platform/x86/asus-laptop.c b/drivers/platform/x86/asus-laptop.c
> > > index 9a69734..15f1311 100644
> > > --- a/drivers/platform/x86/asus-laptop.c
> > > +++ b/drivers/platform/x86/asus-laptop.c
> > > @@ -775,8 +775,10 @@ static int asus_read_brightness(struct backlight_device *bd)
> > >
> > > rv = acpi_evaluate_integer(asus->handle, METHOD_BRIGHTNESS_GET,
> > > NULL, &value);
> > > - if (ACPI_FAILURE(rv))
> > > + if (ACPI_FAILURE(rv)) {
> > > pr_warn("Error reading brightness\n");
> > > + return 0;
> > > + }
> >
> > This looks like a workaround.
> > I suppose the real fix is to return here an error code and fix all callers, like
> > drivers/video/backlight/backlight.c.
> >
>
> It just fixes the behaviour according to the current code in that file. I
> suppose that would be nice but I don't think it would make any difference
> because the backlight core code still prints out ->props.brightness in case
> ops->get_brightness fails. Just the difference would be that now actual error
> messages are printed in the drivers themselves instead of generic messages from
> the backlight core. Anyway, I think the current behaviour is more useful because
> the drivers know better about what has failed.
>
As a matter of practice, based on feedback from the previous pdx86 maintainers,
I prefer to accept patches which fix an immediate issue and leave the rework or
broader work as a follow-on, or a TODO item.
We should look for a good place to document these TODOs.
Queued for 4.7.
Thanks,
--
Darren Hart
Intel Open Source Technology Center