[PATCH next] drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()

[PATCH next] drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()

[Dan Carpenter]

The devm_drm_panel_alloc() function never returns NULL, it returns error
pointers on failure.

Fixes: a7c61963b727 ("drm/panel: Add Himax HX83121A panel driver")
Signed-off-by: Dan Carpenter <error27@gmail.com>
---
This email is a free service from the Smatch-CI project [smatch.sf.net].

 drivers/gpu/drm/panel/panel-himax-hx83121a.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-himax-hx83121a.c b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
index ebe643ba4184..bed79aa06f46 100644
--- a/drivers/gpu/drm/panel/panel-himax-hx83121a.c
+++ b/drivers/gpu/drm/panel/panel-himax-hx83121a.c
@@ -596,8 +596,8 @@ static int himax_probe(struct mipi_dsi_device *dsi)
 
 	ctx = devm_drm_panel_alloc(dev, struct himax, panel, &himax_panel_funcs,
 				   DRM_MODE_CONNECTOR_DSI);
-	if (!ctx)
-		return -ENOMEM;
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
 
 	ret = devm_regulator_bulk_get_const(&dsi->dev,
 					    ARRAY_SIZE(himax_supplies),
-- 
2.53.0

Re: [PATCH next] drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()

[Pengyu Luo]

On Fri, Apr 10, 2026 at 6:12 PM Dan Carpenter <error27@gmail.com> wrote:
>
> The devm_drm_panel_alloc() function never returns NULL, it returns error
> pointers on failure.
>
> Fixes: a7c61963b727 ("drm/panel: Add Himax HX83121A panel driver")
> Signed-off-by: Dan Carpenter <error27@gmail.com>
> ---

Sorry, Chen Ni had sent it.
https://lore.kernel.org/dri-devel/20260327021728.647182-1-nichen@iscas.ac.cn/

--
Pengyu

Claude review: drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()

[Claude Code Review Bot]

Overall Series Review

Subject: drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()
Author: Dan Carpenter <error27@gmail.com>
Patches: 2
Reviewed: 2026-04-12T09:51:38.596947

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This is a single-patch fix from Dan Carpenter / Smatch-CI that corrects an error-checking bug in the himax-hx83121a panel driver's probe function. The fix is straightforward, correct, and well-justified.

The `devm_drm_panel_alloc()` macro wraps `__devm_drm_panel_alloc()`, which is documented in `include/drm/drm_panel.h:316` as returning "Pointer to container structure embedding the panel, **ERR_PTR on failure**." The original code incorrectly checks for `NULL` return, which can never happen — a failure would return an `ERR_PTR`, which is non-NULL and would sail past the `!ctx` check, leading to a crash or undefined behavior when the error pointer is subsequently dereferenced.

**Verdict: Patch looks good. Recommend applying.**

---
Generated by Claude Code Patch Reviewer

Claude review: drm/panel: himax-hx83121a: Fix NULL vs IS_ERR() check in probe()

[Claude Code Review Bot]

Patch Review

**Correctness: Good.** The fix changes:
```c
-	if (!ctx)
-		return -ENOMEM;
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
```

This is correct. The `devm_drm_panel_alloc()` header documentation at `include/drm/drm_panel.h:316` explicitly states it returns `ERR_PTR on failure`, never `NULL`. Using `IS_ERR()` / `PTR_ERR()` is the proper pattern, and is consistent with all other error checks in the same probe function (lines 609, 635, 650 all use `IS_ERR()`).

**Fixes tag:** The `Fixes:` tag referencing `a7c61963b727 ("drm/panel: Add Himax HX83121A panel driver")` is appropriate since the bug was introduced with the original driver addition.

**No issues found.** Clean, minimal, correct fix.

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Generated by Claude Code Patch Reviewer