Fix return code check for "max brightness" ACPI call.
The dell laptop ACPI video brightness control is not present on dell
laptops anymore, but was present in older kernel versions.
The code that checks the return value is incorrect since the SMM
refactoring.
The old code was:
if (buffer->output[0] == 0)
Which was changed to:
ret = dell_send_request(...)
if (ret)
However, dell_send_request() will return 0 if buffer->output[0] == 0,
so we must change the check to:
if (ret == 0)
This issue was found on a Dell M4800 laptop, and the fix tested on it
as well.
Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
Signed-off-by: Damien Thébault <[email protected]>
Tested-by: Damien Thébault <[email protected]>
---
drivers/platform/x86/dell-laptop.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/x86/dell-laptop.c
b/drivers/platform/x86/dell-laptop.c index f1fa8612db40..06978c14c83b
100644 --- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -2185,7 +2185,7 @@ static int __init dell_init(void)
dell_fill_request(&buffer, token->location, 0, 0, 0);
ret = dell_send_request(&buffer,
CLASS_TOKEN_READ,
SELECT_TOKEN_AC);
- if (ret)
+ if (ret == 0)
max_intensity = buffer.output[3];
}
--
2.17.1
On Sunday 08 July 2018 17:02:20 Damien Thébault wrote:
> Fix return code check for "max brightness" ACPI call.
>
> The dell laptop ACPI video brightness control is not present on dell
> laptops anymore, but was present in older kernel versions.
>
> The code that checks the return value is incorrect since the SMM
> refactoring.
>
> The old code was:
> if (buffer->output[0] == 0)
>
> Which was changed to:
> ret = dell_send_request(...)
> if (ret)
>
> However, dell_send_request() will return 0 if buffer->output[0] == 0,
> so we must change the check to:
> if (ret == 0)
You are right, dell_send_request() return non-zero value on error.
> This issue was found on a Dell M4800 laptop, and the fix tested on it
> as well.
>
> Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
> Signed-off-by: Damien Thébault <[email protected]>
> Tested-by: Damien Thébault <[email protected]>
> ---
> drivers/platform/x86/dell-laptop.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c
> b/drivers/platform/x86/dell-laptop.c index f1fa8612db40..06978c14c83b
> 100644 --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -2185,7 +2185,7 @@ static int __init dell_init(void)
> dell_fill_request(&buffer, token->location, 0, 0, 0);
> ret = dell_send_request(&buffer,
> CLASS_TOKEN_READ,
> SELECT_TOKEN_AC);
> - if (ret)
> + if (ret == 0)
> max_intensity = buffer.output[3];
> }
>
Reviewed-by: Pali Rohár <[email protected]>
--
Pali Rohár
[email protected]
> -----Original Message-----
> From: Pali Rohár [mailto:[email protected]]
> Sent: Sunday, July 8, 2018 8:09 AM
> To: Damien Thébault
> Cc: Matthew Garrett; Darren Hart; Andy Shevchenko; Limonciello, Mario; platform-
> [email protected]; [email protected]
> Subject: Re: [PATCH] dell-laptop: Fix backlight detection
>
> On Sunday 08 July 2018 17:02:20 Damien Thébault wrote:
> > Fix return code check for "max brightness" ACPI call.
> >
> > The dell laptop ACPI video brightness control is not present on dell
> > laptops anymore, but was present in older kernel versions.
> >
> > The code that checks the return value is incorrect since the SMM
> > refactoring.
> >
> > The old code was:
> > if (buffer->output[0] == 0)
> >
> > Which was changed to:
> > ret = dell_send_request(...)
> > if (ret)
> >
> > However, dell_send_request() will return 0 if buffer->output[0] == 0,
> > so we must change the check to:
> > if (ret == 0)
>
> You are right, dell_send_request() return non-zero value on error.
>
> > This issue was found on a Dell M4800 laptop, and the fix tested on it
> > as well.
> >
> > Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
> > Signed-off-by: Damien Thébault <[email protected]>
> > Tested-by: Damien Thébault <[email protected]>
> > ---
> > drivers/platform/x86/dell-laptop.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/dell-laptop.c
> > b/drivers/platform/x86/dell-laptop.c index f1fa8612db40..06978c14c83b
> > 100644 --- a/drivers/platform/x86/dell-laptop.c
> > +++ b/drivers/platform/x86/dell-laptop.c
> > @@ -2185,7 +2185,7 @@ static int __init dell_init(void)
> > dell_fill_request(&buffer, token->location, 0, 0, 0);
> > ret = dell_send_request(&buffer,
> > CLASS_TOKEN_READ,
> > SELECT_TOKEN_AC);
> > - if (ret)
> > + if (ret == 0)
> > max_intensity = buffer.output[3];
> > }
> >
>
> Reviewed-by: Pali Rohár <[email protected]>
>
Thanks for this catch.
Reviewed-by: Mario Limonciello <[email protected]>
This should probably go to stable as well.
On Sun, Jul 08, 2018 at 05:02:20PM +0200, Damien Th?bault wrote:
> Fix return code check for "max brightness" ACPI call.
>
> The dell laptop ACPI video brightness control is not present on dell
> laptops anymore, but was present in older kernel versions.
>
> The code that checks the return value is incorrect since the SMM
> refactoring.
>
> The old code was:
> if (buffer->output[0] == 0)
>
> Which was changed to:
> ret = dell_send_request(...)
> if (ret)
>
> However, dell_send_request() will return 0 if buffer->output[0] == 0,
> so we must change the check to:
> if (ret == 0)
>
> This issue was found on a Dell M4800 laptop, and the fix tested on it
> as well.
>
> Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
> Signed-off-by: Damien Th?bault <[email protected]>
> Tested-by: Damien Th?bault <[email protected]>
Thanks for the analysis and fix Damien.
I was unable to apply the patch. Apparently due to your Content-Tranfer-Encoding
being set to "quoted-printable". This converts "=" characters to =3D.
Please work with your mail client and try sending the patch
to yourself and applying it. Once that works, please resend.
I suspect you may need to do one or both of the following:
- Disable preferences->compose->"wrap pasted text" (or whichever applies to how
you get the patch into the compose window)
- Set Preferences->Mail Handling->Sending->Transfer Encoding to 8bit to avoid
"quoted-printable".
Other claws users who send patches have Content-Transfer-Encoding set to 7bit
Thanks,
> ---
> drivers/platform/x86/dell-laptop.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c
> b/drivers/platform/x86/dell-laptop.c index f1fa8612db40..06978c14c83b
> 100644 --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -2185,7 +2185,7 @@ static int __init dell_init(void)
> dell_fill_request(&buffer, token->location, 0, 0, 0);
> ret = dell_send_request(&buffer,
> CLASS_TOKEN_READ,
> SELECT_TOKEN_AC);
> - if (ret)
> + if (ret == 0)
> max_intensity = buffer.output[3];
> }
>
> --
> 2.17.1
>
--
Darren Hart
VMware Open Source Technology Center