[PATCH] drm/sharp-memory: Fix IS_ERR() vs NULL check in sharp_memory_probe()

[PATCH] drm/sharp-memory: Fix IS_ERR() vs NULL check in sharp_memory_probe()

[Chen Ni]

The devm_drm_dev_alloc() function returns an ERR_PTR encoded error
pointer on failure, not NULL. devm_gpiod_get_optional() may return
ERR_PTR in case of genuine GPIO acquisition errors, not just NULL which
indicates the legitimate absence of an optional GPIO.

Replace the NULL check after devm_drm_dev_alloc() with IS_ERR() and add
a missing IS_ERR() check after devm_gpiod_get_optional(). On error,
return the error code from the probe function to ensure proper failure
handling rather than proceeding with invalid pointers.

Fixes: b8f9f21716fe ("drm/tiny: Add driver for Sharp Memory LCD")
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
---
 drivers/gpu/drm/tiny/sharp-memory.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tiny/sharp-memory.c b/drivers/gpu/drm/tiny/sharp-memory.c
index 64272cd0f6e2..5e6a54a0696c 100644
--- a/drivers/gpu/drm/tiny/sharp-memory.c
+++ b/drivers/gpu/drm/tiny/sharp-memory.c
@@ -541,8 +541,9 @@ static int sharp_memory_probe(struct spi_device *spi)
 
 	smd = devm_drm_dev_alloc(dev, &sharp_memory_drm_driver,
 				 struct sharp_memory_device, drm);
-	if (!smd)
-		return -ENOMEM;
+	if (IS_ERR(smd))
+		return dev_err_probe(dev, PTR_ERR(smd),
+				     "Failed to allocate drm device\n");
 
 	spi_set_drvdata(spi, smd);
 
@@ -553,6 +554,9 @@ static int sharp_memory_probe(struct spi_device *spi)
 		return dev_err_probe(dev, ret, "Failed to initialize drm config\n");
 
 	smd->enable_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(smd->enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(smd->enable_gpio),
+				     "Failed to get gpio 'enable'\n");
 	if (!smd->enable_gpio)
 		dev_warn(dev, "Enable gpio not defined\n");
 
-- 
2.25.1

Re: [PATCH] drm/sharp-memory: Fix IS_ERR() vs NULL check in sharp_memory_probe()

[Markus Elfring]

…
> Replace the NULL check after devm_drm_dev_alloc() with IS_ERR()

May extra error messages be omitted for selected allocation failures?



>                                                                 and add
> a missing IS_ERR() check after devm_gpiod_get_optional(). On error,
> return the error code from the probe function to ensure proper failure
> handling rather than proceeding with invalid pointers.

* Were any source code analysis tools involved here?

* Did anything hinder to add any tags (like “Fixes” and “Cc”) accordingly?


Regards,
Markus