Hi Arnd,
On Mon, Oct 24, 2016 at 05:32:08PM +0200, Arnd Bergmann wrote:
> Older versions of gcc warn about the tca8418_irq_handler function
> as they can't keep track of the variable assignment inside of the
> loop when using the -Wmaybe-unintialized flag:
>
> drivers/input/keyboard/tca8418_keypad.c: In function ‘tca8418_irq_handler’:
> drivers/input/keyboard/tca8418_keypad.c:172:9: error: ‘reg’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> drivers/input/keyboard/tca8418_keypad.c:165:5: note: ‘reg’ was declared here
>
> This is fixed in gcc-6, but it's possible to rearrange the code
> in a way that avoids the warning on older compilers as well.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> drivers/input/keyboard/tca8418_keypad.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/input/keyboard/tca8418_keypad.c b/drivers/input/keyboard/tca8418_keypad.c
> index 9002298698fc..3048ef3e3e16 100644
> --- a/drivers/input/keyboard/tca8418_keypad.c
> +++ b/drivers/input/keyboard/tca8418_keypad.c
> @@ -164,11 +164,18 @@ static void tca8418_read_keypad(struct tca8418_keypad *keypad_data)
> int error, col, row;
> u8 reg, state, code;
>
> - /* Initial read of the key event FIFO */
> - error = tca8418_read_byte(keypad_data, REG_KEY_EVENT_A, ®);
> + do {
> + error = tca8418_read_byte(keypad_data, REG_KEY_EVENT_A, ®);
> + if (error < 0) {
> + dev_err(&keypad_data->client->dev,
> + "unable to read REG_KEY_EVENT_A\n");
> + break;
> + }
> +
> + /* Assume that key code 0 signifies empty FIFO */
> + if (reg <= 0)
> + break;
I am unconvinced that this rearrangement fixes the issue for all older
GCCs. Can we simply do:
u8 uninitialized_var(reg);
and be done with it?
Thanks.
--
Dmitry
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