From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] Input: tca8418_keypad: hide gcc-4.9 -Wmaybe-uninitialized warning Date: Mon, 24 Oct 2016 16:45:13 -0700 Message-ID: <20161024234513.GA15034@dtor-ws> References: <20161024153222.2738294-1-arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20161024153222.2738294-1-arnd@arndb.de> Sender: linux-kernel-owner@vger.kernel.org To: Arnd Bergmann Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-input@vger.kernel.org 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 > --- > 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