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serial: ifx6x60: avoid uninitialized variable use

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gcc warns about a potential use of an uninitialized variable in this driver:

drivers/tty/serial/ifx6x60.c: In function 'ifx_spi_complete':
drivers/tty/serial/ifx6x60.c:713:6: warning: 'more' may be used uninitialized in this function [-Wmaybe-uninitialized]
   if (more || ifx_dev->spi_more || queue_length > 0 ||

Unlike a lot of other such warnings, this one is correct and describes
an actual problem in the handling of the "IFX_SPI_HEADER_F" result code.

This appears to be a result from a restructuring of the driver that
dates back to before it was merged in the kernel, so it's impossible
to know where it went wrong. I also don't know what that result code
means, so I have no idea if setting 'more' to zero is the correct
solution, but at least it makes the behavior reproducible rather than
depending on whatever happens to be on the kernel stack.

This patch initializes the 'more' variable to zero in each of the
three code paths that could result in undefined behavior before,
which is more explicit than initializing it at the start of the
function.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Arnd Bergmann 2016-02-25 21:47:57 +01:00 committed by Greg Kroah-Hartman
parent 2958ccee36
commit 0b8053fef6
1 changed files with 3 additions and 0 deletions
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3
drivers/tty/serial/ifx6x60.c
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@ -395,8 +395,10 @@ static int ifx_spi_decode_spi_header(unsigned char *buffer, int *length,
if (h1 == 0 && h2 == 0) {
*received_cts = 0;
*more = 0;
return IFX_SPI_HEADER_0;
} else if (h1 == 0xffff && h2 == 0xffff) {
*more = 0;
/* spi_slave_cts remains as it was */
return IFX_SPI_HEADER_F;
}
@ -688,6 +690,7 @@ static void ifx_spi_complete(void *ctx)
ifx_dev->rx_buffer + IFX_SPI_HEADER_OVERHEAD,
(size_t)actual_length);
} else {
more = 0;
dev_dbg(&ifx_dev->spi_dev->dev, "SPI transfer error %d",
ifx_dev->spi_msg.status);
}