[PATCH] drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[PATCH] drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Mon, 13 Jul 2026 15:56:46 +0200

The address of a data structure member was determined before
a corresponding null pointer check in the implementation of
the function “intel_bios_encoder_supports_dp_dual_mode”.

Thus avoid the risk for undefined behaviour by reducing the scope for
the variable “child” behind condition checks.

This issue was detected by using the Coccinelle software.

Fixes: 044cbc7a74c136f12a80c855cadd1b085084aef1 ("drm/i915/bios: Nuke DEVICE_TYPE_DP_DUAL_MODE_BITS")
Cc: stable@vger.kernel.org
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 drivers/gpu/drm/i915/display/intel_bios.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 97cbae2e547e..1c4760373514 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -3514,8 +3514,6 @@ bool intel_bios_is_port_present(struct intel_display *display, enum port port)
 
 bool intel_bios_encoder_supports_dp_dual_mode(const struct intel_bios_encoder_data *devdata)
 {
-	const struct child_device_config *child = &devdata->child;
-
 	if (!devdata)
 		return false;
 
@@ -3523,6 +3521,8 @@ bool intel_bios_encoder_supports_dp_dual_mode(const struct intel_bios_encoder_da
 	    !intel_bios_encoder_supports_hdmi(devdata))
 		return false;
 
+	const struct child_device_config *child = &devdata->child;
+
 	if (dvo_port_type(child->dvo_port) == DVO_PORT_DPA)
 		return true;
 
-- 
2.55.0

✗ LGCI.VerificationFailed: failure for drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Patchwork]

== Series Details ==

Series: drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()
URL   : https://patchwork.freedesktop.org/series/170414/
State : failure

== Summary ==

Series author address 'markus.elfring@web.de' is not on the allowlist, which prevents CI from being automatically triggered.
If you want CI to run for this series, ask Patchwork project owners to click 'retest' on the series in Patchwork.
Exception occurred during validation, bailing out!
Build URL: http://intel-gfx-ci-public.igk.intel.com:8080/job/xe_pw_trigger/1215553/ (on master)

✗ LGCI.VerificationFailed: failure for drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Patchwork]

== Series Details ==

Series: drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()
URL   : https://patchwork.freedesktop.org/series/170415/
State : failure

== Summary ==

Series author address 'markus.elfring@web.de' is not on the allowlist, which prevents CI from being automatically triggered.
If you want CI to run for this series, ask Patchwork project owners to click 'retest' on the series in Patchwork.
Exception occurred during validation, bailing out!
Build URL: http://gfx-ci.igk.intel.com:8080/job/CI_PW_kernel/181358/ (on built-in)

Re: [PATCH] drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Rodrigo Vivi]

On Mon, Jul 13, 2026 at 04:05:53PM +0200, Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Mon, 13 Jul 2026 15:56:46 +0200
> 
> The address of a data structure member was determined before
> a corresponding null pointer check in the implementation of
> the function “intel_bios_encoder_supports_dp_dual_mode”.
> 
> Thus avoid the risk for undefined behaviour by reducing the scope for
> the variable “child” behind condition checks.
> 
> This issue was detected by using the Coccinelle software.
> 
> Fixes: 044cbc7a74c136f12a80c855cadd1b085084aef1 ("drm/i915/bios: Nuke DEVICE_TYPE_DP_DUAL_MODE_BITS")
> Cc: stable@vger.kernel.org
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  drivers/gpu/drm/i915/display/intel_bios.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index 97cbae2e547e..1c4760373514 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -3514,8 +3514,6 @@ bool intel_bios_is_port_present(struct intel_display *display, enum port port)
>  
>  bool intel_bios_encoder_supports_dp_dual_mode(const struct intel_bios_encoder_data *devdata)
>  {
> -	const struct child_device_config *child = &devdata->child;
> -
>  	if (!devdata)
>  		return false;
>  
> @@ -3523,6 +3521,8 @@ bool intel_bios_encoder_supports_dp_dual_mode(const struct intel_bios_encoder_da
>  	    !intel_bios_encoder_supports_hdmi(devdata))
>  		return false;
>  
> +	const struct child_device_config *child = &devdata->child;
> +

does it compile?

please keep the variable definition where it is and move only its
assignment after the null check.

Thanks,
Rodrigo.

>  	if (dvo_port_type(child->dvo_port) == DVO_PORT_DPA)
>  		return true;
>  
> -- 
> 2.55.0
> 

Re: [PATCH] drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Dan Carpenter]

On Tue, Jul 14, 2026 at 11:28:23AM -0400, Rodrigo Vivi wrote:
> On Mon, Jul 13, 2026 at 04:05:53PM +0200, Markus Elfring wrote:
> > From: Markus Elfring <elfring@users.sourceforge.net>
> > Date: Mon, 13 Jul 2026 15:56:46 +0200
> > 
> > The address of a data structure member was determined before
> > a corresponding null pointer check in the implementation of
> > the function “intel_bios_encoder_supports_dp_dual_mode”.
> > 
> > Thus avoid the risk for undefined behaviour by reducing the scope for
> > the variable “child” behind condition checks.
> > 
> > This issue was detected by using the Coccinelle software.
> > 
> > Fixes: 044cbc7a74c136f12a80c855cadd1b085084aef1 ("drm/i915/bios: Nuke DEVICE_TYPE_DP_DUAL_MODE_BITS")
> > Cc: stable@vger.kernel.org

Please stop adding Fixes tags to these and talking about "undefined
behavior" in the commit message.  Pointer math is defined...  It's
just a style preference on your part.

regards,
dan carpenter

Re: [PATCH] drm/i915/bios: Move a variable assignment behind a null pointer check in intel_bios_encoder_supports_dp_dual_mode()

[Markus Elfring]

>>> The address of a data structure member was determined before
>>> a corresponding null pointer check in the implementation of
>>> the function “intel_bios_encoder_supports_dp_dual_mode”.
>>>
>>> Thus avoid the risk for undefined behaviour by reducing the scope for
>>> the variable “child” behind condition checks.
>>>
>>> This issue was detected by using the Coccinelle software.
>>>
>>> Fixes: 044cbc7a74c136f12a80c855cadd1b085084aef1 ("drm/i915/bios: Nuke DEVICE_TYPE_DP_DUAL_MODE_BITS")
>>> Cc: stable@vger.kernel.org
> 
> Please stop adding Fixes tags to these and talking about "undefined
> behavior" in the commit message.  Pointer math is defined...

What does hinder you to take additional information sources better into account?


> It's just a style preference on your part.
Do you find the guidance appropriate according to the SEI CERT C Coding Standard?
https://cmu-sei.github.io/secure-coding-standards/sei-cert-c-coding-standard/rules/expressions-exp/exp34-c/

Regards,
Markus