[PATCH v2 0/2] drm: Make some resolution info unsigned

[PATCH v2 0/2] drm: Make some resolution info unsigned

[Lyude Paul]

During the review of some of my patches for KMS bindings in Rust, it was
pointed out we have some areas of DRM that are storing resolutions as
signed integers when it doesn't really make sense. Since Rust has
arithematic overflow checking by default in the kernel, let's change
these to unsigned so that we can take advantage of that.

Lyude Paul (2):
  drm/edid: Use unsigned int in drm_add_modes_noedid()
  drm/mode_config: Make drm_mode_config.(max|min)_(width|height)
    unsigned

 drivers/gpu/drm/drm_edid.c    | 10 ++--------
 include/drm/drm_edid.h        |  2 +-
 include/drm/drm_mode_config.h |  4 ++--
 3 files changed, 5 insertions(+), 11 deletions(-)


base-commit: cf05922d63e2ae6a9b1b52ff5236a44c3b29f78c
-- 
2.48.1

[PATCH v2 1/2] drm/edid: Use unsigned int in drm_add_modes_noedid()

[Lyude Paul]

A negative resolution doesn't really make any sense, so let's make these
parameters unsigned. In C this doesn't make much of a difference, but Rust
is stricter about signed/unsigned casts and additionally can check for
arithmetic over/underflows if CONFIG_RUST_OVERFLOW_CHECKS is enabled.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>

---

V2:
* Remove h/vdisplay < 0 checks in drm_add_modes_noedid()

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_edid.c | 10 ++--------
 include/drm/drm_edid.h     |  2 +-
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 13bc4c290b17d..1e69326283dce 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -7099,18 +7099,12 @@ EXPORT_SYMBOL(drm_add_edid_modes);
  * Return: The number of modes added or 0 if we couldn't find any.
  */
 int drm_add_modes_noedid(struct drm_connector *connector,
-			int hdisplay, int vdisplay)
+			 unsigned int hdisplay, unsigned int vdisplay)
 {
-	int i, count, num_modes = 0;
+	int i, count = ARRAY_SIZE(drm_dmt_modes), num_modes = 0;
 	struct drm_display_mode *mode;
 	struct drm_device *dev = connector->dev;
 
-	count = ARRAY_SIZE(drm_dmt_modes);
-	if (hdisplay < 0)
-		hdisplay = 0;
-	if (vdisplay < 0)
-		vdisplay = 0;
-
 	for (i = 0; i < count; i++) {
 		const struct drm_display_mode *ptr = &drm_dmt_modes[i];
 
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index eaac5e665892a..b38409670868d 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -437,7 +437,7 @@ bool drm_detect_monitor_audio(const struct edid *edid);
 enum hdmi_quantization_range
 drm_default_rgb_quant_range(const struct drm_display_mode *mode);
 int drm_add_modes_noedid(struct drm_connector *connector,
-			 int hdisplay, int vdisplay);
+			 unsigned int hdisplay, unsigned int vdisplay);
 
 int drm_edid_header_is_valid(const void *edid);
 bool drm_edid_is_valid(struct edid *edid);
-- 
2.48.1

[PATCH v2 2/2] drm/mode_config: Make drm_mode_config.(max|min)_(width|height) unsigned

[Lyude Paul]

It doesn't make much sense to allow devices to specify their min/max
resolution as signed integers, and in Rust with CONFIG_RUST_OVERFLOW_CHECKS
enabled this provides us actual over/underflow checks. Similarly, it
doesn't really make much sense for us to allow devices to specify their
minimum/maximum resolution as signed.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>

---

V2:
* No functional changes, just update the commit message w/r/t Thomas's
  comments.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 include/drm/drm_mode_config.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
index 271765e2e9f2d..4b8f0370b79bf 100644
--- a/include/drm/drm_mode_config.h
+++ b/include/drm/drm_mode_config.h
@@ -532,8 +532,8 @@ struct drm_mode_config {
 	 */
 	struct list_head privobj_list;
 
-	int min_width, min_height;
-	int max_width, max_height;
+	unsigned int min_width, min_height;
+	unsigned int max_width, max_height;
 	const struct drm_mode_config_funcs *funcs;
 
 	/* output poll support */
-- 
2.48.1

Re: [PATCH v2 0/2] drm: Make some resolution info unsigned

[Thomas Zimmermann]

Hi

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

for the series.

Best regards
Thomas

Am 01.04.25 um 00:23 schrieb Lyude Paul:
> During the review of some of my patches for KMS bindings in Rust, it was
> pointed out we have some areas of DRM that are storing resolutions as
> signed integers when it doesn't really make sense. Since Rust has
> arithematic overflow checking by default in the kernel, let's change
> these to unsigned so that we can take advantage of that.
>
> Lyude Paul (2):
>    drm/edid: Use unsigned int in drm_add_modes_noedid()
>    drm/mode_config: Make drm_mode_config.(max|min)_(width|height)
>      unsigned
>
>   drivers/gpu/drm/drm_edid.c    | 10 ++--------
>   include/drm/drm_edid.h        |  2 +-
>   include/drm/drm_mode_config.h |  4 ++--
>   3 files changed, 5 insertions(+), 11 deletions(-)
>
>
> base-commit: cf05922d63e2ae6a9b1b52ff5236a44c3b29f78c

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)