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

[kbuild test robot]

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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