Re: [PATCH 4/8] gpio: pcie-idio-24: Implement get_multiple callback

[kbuild test robot <lkp@xxxxxxxxx>]

Hi William,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.16-rc5 next-20180313]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Implement-get_multiple-for-ACCES-and-PC104-drivers/20180313-202244
config: x86_64-randconfig-x014-201810 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers//gpio/gpio-pcie-idio-24.c: In function 'idio_24_gpio_get_multiple':
>> drivers//gpio/gpio-pcie-idio-24.c:252:35: warning: 'port_state' may be used uninitialized in this function [-Wmaybe-uninitialized]
      bits[BIT_WORD(i)] |= port_state << bit_word_offset;
                           ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~

vim +/port_state +252 drivers//gpio/gpio-pcie-idio-24.c

   195	
   196	static int idio_24_gpio_get_multiple(struct gpio_chip *chip,
   197		unsigned long *mask, unsigned long *bits)
   198	{
   199		struct idio_24_gpio *const idio24gpio = gpiochip_get_data(chip);
   200		struct idio_24_gpio_reg __iomem *const reg = idio24gpio->reg;
   201		unsigned int i;
   202		const unsigned int gpio_reg_size = 8;
   203		unsigned int bit_word_offset;
   204		unsigned int bits_mask;
   205		const unsigned long reg_mask = GENMASK(gpio_reg_size, 0);
   206		unsigned long port_state;
   207		const unsigned long out_mode_mask = BIT(1);
   208	
   209		/* clear bits array to a clean slate */
   210		for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
   211			bits[i / BITS_PER_LONG] = 0;
   212	
   213		/* get bits are evaluated a gpio register size at a time */
   214		for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
   215			bit_word_offset = i % BITS_PER_LONG;
   216			bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
   217			if (!bits_mask) {
   218				/* no get bits in this register so skip to next one */
   219				continue;
   220			}
   221	
   222			/* read bits from current gpio register */
   223			switch (i / gpio_reg_size) {
   224			case 0:
   225				port_state = ioread8(&reg->out0_7);
   226				break;
   227			case 1:
   228				port_state = ioread8(&reg->out8_15);
   229				break;
   230			case 2:
   231				port_state = ioread8(&reg->out16_23);
   232				break;
   233			case 3:
   234				port_state = ioread8(&reg->in0_7);
   235				break;
   236			case 4:
   237				port_state = ioread8(&reg->in8_15);
   238				break;
   239			case 5:
   240				port_state = ioread8(&reg->in16_23);
   241				break;
   242			case 6:
   243				/* TTL/CMOS Outputs/Inputs */
   244				if (ioread8(&reg->ctl) & out_mode_mask)
   245					port_state = ioread8(&reg->ttl_out0_7);
   246				else
   247					port_state = ioread8(&reg->ttl_in0_7);
   248				break;
   249			}
   250	
   251			/* store acquired bits */
 > 252			bits[BIT_WORD(i)] |= port_state << bit_word_offset;
   253		}
   254	
   255		return 0;
   256	}
   257	

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