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SubjectRe: [PATCH 3/8] gpio: pci-idio-16: Implement get_multiple callback
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-x015-201810 (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-pci-idio-16.c: In function 'idio_16_gpio_get_multiple':
>> drivers//gpio/gpio-pci-idio-16.c:147:35: warning: 'port_state' may be used uninitialized in this function [-Wmaybe-uninitialized]
bits[BIT_WORD(i)] |= port_state << bit_word_offset;
~~~~~~~~~~~^~~~~~~~~~~~~~~~~~

vim +/port_state +147 drivers//gpio/gpio-pci-idio-16.c

105
106 static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
107 unsigned long *mask, unsigned long *bits)
108 {
109 struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
110 unsigned int i;
111 const unsigned int gpio_reg_size = 8;
112 unsigned int bit_word_offset;
113 unsigned int bits_mask;
114 const unsigned long reg_mask = GENMASK(gpio_reg_size, 0);
115 unsigned long port_state;
116
117 /* clear bits array to a clean slate */
118 for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
119 bits[i / BITS_PER_LONG] = 0;
120
121 /* get bits are evaluated a gpio register size at a time */
122 for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
123 bit_word_offset = i % BITS_PER_LONG;
124 bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
125 if (!bits_mask) {
126 /* no get bits in this register so skip to next one */
127 continue;
128 }
129
130 /* read bits from current gpio register */
131 switch (i / gpio_reg_size) {
132 case 0:
133 port_state = ioread8(&idio16gpio->reg->out0_7);
134 break;
135 case 1:
136 port_state = ioread8(&idio16gpio->reg->out8_15);
137 break;
138 case 2:
139 port_state = ioread8(&idio16gpio->reg->in0_7);
140 break;
141 case 3:
142 port_state = ioread8(&idio16gpio->reg->in8_15);
143 break;
144 }
145
146 /* store acquired bits */
> 147 bits[BIT_WORD(i)] |= port_state << bit_word_offset;
148 }
149
150 return 0;
151 }
152

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