drivers/net/dsa/microchip/ksz_ptp.c:217 ksz_ptp_clock_register() warn: passing zero to 'PTR_ERR'

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   fa31fc82fb775445c176e576304c4098222f47f2
commit: eac1ea20261e1fac8ffbfb3b7da2d5e6b7c159e3 net: dsa: microchip: ptp: add the posix clock support
config: openrisc-randconfig-m031-20230430 (https://download.01.org/0day-ci/archive/20230504/202305041244.tDo9luPw-lkp@xxxxxxxxx/config)
compiler: or1k-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>
| Link: https://lore.kernel.org/r/202305041244.tDo9luPw-lkp@xxxxxxxxx/

smatch warnings:
drivers/net/dsa/microchip/ksz_ptp.c:217 ksz_ptp_clock_register() warn: passing zero to 'PTR_ERR'

vim +/PTR_ERR +217 drivers/net/dsa/microchip/ksz_ptp.c

eac1ea20261e1f Christian Eggers 2023-01-10  186  int ksz_ptp_clock_register(struct dsa_switch *ds)
eac1ea20261e1f Christian Eggers 2023-01-10  187  {
eac1ea20261e1f Christian Eggers 2023-01-10  188  	struct ksz_device *dev = ds->priv;
eac1ea20261e1f Christian Eggers 2023-01-10  189  	struct ksz_ptp_data *ptp_data;
eac1ea20261e1f Christian Eggers 2023-01-10  190  	int ret;
eac1ea20261e1f Christian Eggers 2023-01-10  191  
eac1ea20261e1f Christian Eggers 2023-01-10  192  	ptp_data = &dev->ptp_data;
eac1ea20261e1f Christian Eggers 2023-01-10  193  	mutex_init(&ptp_data->lock);
eac1ea20261e1f Christian Eggers 2023-01-10  194  
eac1ea20261e1f Christian Eggers 2023-01-10  195  	ptp_data->caps.owner		= THIS_MODULE;
eac1ea20261e1f Christian Eggers 2023-01-10  196  	snprintf(ptp_data->caps.name, 16, "Microchip Clock");
eac1ea20261e1f Christian Eggers 2023-01-10  197  	ptp_data->caps.max_adj		= KSZ_MAX_DRIFT_CORR;
eac1ea20261e1f Christian Eggers 2023-01-10  198  	ptp_data->caps.gettime64	= ksz_ptp_gettime;
eac1ea20261e1f Christian Eggers 2023-01-10  199  	ptp_data->caps.settime64	= ksz_ptp_settime;
eac1ea20261e1f Christian Eggers 2023-01-10  200  	ptp_data->caps.adjfine		= ksz_ptp_adjfine;
eac1ea20261e1f Christian Eggers 2023-01-10  201  	ptp_data->caps.adjtime		= ksz_ptp_adjtime;
eac1ea20261e1f Christian Eggers 2023-01-10  202  
eac1ea20261e1f Christian Eggers 2023-01-10  203  	ret = ksz_ptp_start_clock(dev);
eac1ea20261e1f Christian Eggers 2023-01-10  204  	if (ret)
eac1ea20261e1f Christian Eggers 2023-01-10  205  		return ret;
eac1ea20261e1f Christian Eggers 2023-01-10  206  
eac1ea20261e1f Christian Eggers 2023-01-10  207  	/* Currently only P2P mode is supported. When 802_1AS bit is set, it
eac1ea20261e1f Christian Eggers 2023-01-10  208  	 * forwards all PTP packets to host port and none to other ports.
eac1ea20261e1f Christian Eggers 2023-01-10  209  	 */
eac1ea20261e1f Christian Eggers 2023-01-10  210  	ret = ksz_rmw16(dev, REG_PTP_MSG_CONF1, PTP_TC_P2P | PTP_802_1AS,
eac1ea20261e1f Christian Eggers 2023-01-10  211  			PTP_TC_P2P | PTP_802_1AS);
eac1ea20261e1f Christian Eggers 2023-01-10  212  	if (ret)
eac1ea20261e1f Christian Eggers 2023-01-10  213  		return ret;
eac1ea20261e1f Christian Eggers 2023-01-10  214  
eac1ea20261e1f Christian Eggers 2023-01-10  215  	ptp_data->clock = ptp_clock_register(&ptp_data->caps, dev->dev);
eac1ea20261e1f Christian Eggers 2023-01-10  216  	if (IS_ERR_OR_NULL(ptp_data->clock))
eac1ea20261e1f Christian Eggers 2023-01-10 @217  		return PTR_ERR(ptp_data->clock);


PTR_ERR(NULL) is success.

This code suggests that ptp_clock_register() is required.  If it is
required then it should be enforced by the .config instead of leaving
the user with a module that can never be probed.

However, if it's not absolutely required and the user is allowed to
disable it in their .config then the way to write it is:

	ptp_data->clock = ptp_clock_register(&ptp_data->caps, dev->dev);
	if (IS_ERR(ptp_data->clock))
		return PTR_ERR(ptp_data->clock);

Just add NULL checks before every ptp_data->clock dereference inside the
driver.  (All the clock functions will be no-ops at that point so don't
worry about them).

See my blog for more info:
https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/

eac1ea20261e1f Christian Eggers 2023-01-10  218  
eac1ea20261e1f Christian Eggers 2023-01-10  219  	return 0;
eac1ea20261e1f Christian Eggers 2023-01-10  220  }

-- 
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https://github.com/intel/lkp-tests