[PATCH v8 10/15] cpufreq: Add Kryo CPU scaling driver

On Sat, May 19, 2018 at 02:09:24PM +0300, ilialin at codeaurora.org wrote:

+static int __init qcom_cpufreq_kryo_driver_init(void)
+{
+       struct device *cpu_dev_silver, *cpu_dev_gold;
+       struct opp_table *opp_silver, *opp_gold;
+       enum _msm8996_version msm8996_version;
+       struct nvmem_cell *speedbin_nvmem;
+       struct platform_device *pdev;
+       struct device_node *np;
+       u8 *speedbin;
+       u32 versions;
+       size_t len;
+       int ret;
+
+       cpu_dev_silver = get_cpu_device(SILVER_LEAD);
+       if (IS_ERR_OR_NULL(cpu_dev_silver))
+               return PTR_ERR(cpu_dev_silver);
+
+       cpu_dev_gold = get_cpu_device(SILVER_LEAD);
+       if (IS_ERR_OR_NULL(cpu_dev_gold))
+               return PTR_ERR(cpu_dev_gold);
+
+       msm8996_version = qcom_cpufreq_kryo_get_msm_id();
+       if (NUM_OF_MSM8996_VERSIONS == msm8996_version) {
+               dev_err(cpu_dev_silver, "Not Snapdragon 820/821!");
+               return -ENODEV;
+       }
+
+       np = dev_pm_opp_of_get_opp_desc_node(cpu_dev_silver);
+       if (IS_ERR_OR_NULL(np))
+               return PTR_ERR(np);

This function (qcom_cpufreq_kryo_driver_init) returns zero on success.
You are checking "np" here for being an error pointer, or NULL.
What value do you think PTR_ERR() returns in the case of PTR_ERR(NULL)?

IS_ERR_OR_NULL() is considered by some (me included) as being _very_
harmful because programmers generally fail to look at linux/err.h and
consider what it means when used as above.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up