[Nouveau] [bug report] drm/nouveau/hwmon: Remove old code, add .write/.read operations

From: Dan Carpenter <dan.carpenter@oracle.com>
To: osalvador.vilardaga@gmail.com
Cc: nouveau@lists.freedesktop.org
Subject: [Nouveau] [bug report] drm/nouveau/hwmon: Remove old code, add .write/.read operations
Date: Wed, 21 Apr 2021 16:24:09 +0300	[thread overview]
Message-ID: <YIAneTPoxr5n7485@mwanda> (raw)

Hello Oscar Salvador,

The patch bfb96e4c344e: "drm/nouveau/hwmon: Remove old code, add
.write/.read operations" from May 18, 2017, leads to the following
static checker warning:

    drivers/gpu/drm/nouveau/nouveau_hwmon.c:507 nouveau_in_read()
    warn: check sign expansion for '-19'
    drivers/gpu/drm/nouveau/nouveau_hwmon.c:510 nouveau_in_read()
    warn: check sign expansion for '-19'

drivers/gpu/drm/nouveau/nouveau_hwmon.c
   488  static int
   489  nouveau_in_read(struct device *dev, u32 attr, int channel, long *val)
   490  {
   491          struct drm_device *drm_dev = dev_get_drvdata(dev);
   492          struct nouveau_drm *drm = nouveau_drm(drm_dev);
   493          struct nvkm_volt *volt = nvxx_volt(&drm->client.device);
   494          int ret;
   495  
   496          if (!volt)
   497                  return -EOPNOTSUPP;
   498  
   499          switch (attr) {
   500          case hwmon_in_input:
   501                  if (drm_dev->switch_power_state != DRM_SWITCH_POWER_ON)
   502                          return -EINVAL;
   503                  ret = nvkm_volt_get(volt);
   504                  *val = ret < 0 ? ret : (ret / 1000);
   505                  break;
   506          case hwmon_in_min:
   507                  *val = volt->min_uv > 0 ? (volt->min_uv / 1000) : -ENODEV;

This is trying to set "*val = -ENODEV" but because "volt->min_uv" is
unsigned int it actually sets it to "*val = (unsigned int)-ENODEV".

It's weird to me that this code doesn't return -ENODEV instead of
setting *val to it.

   508                  break;
   509          case hwmon_in_max:
   510                  *val = volt->max_uv > 0 ? (volt->max_uv / 1000) : -ENODEV;
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

   511                  break;
   512          default:
   513                  return -EOPNOTSUPP;
   514          }
   515  
   516          return 0;
   517  }

regards,
dan carpenter
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