linux-kernel - Re: [PATCH] mtd: spi-nor: stm32-quadspi: avoid unintialized return code

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Date:   Thu, 14 Sep 2017 14:38:51 +0200
From:   Ludovic BARRE <ludovic.barre@...com>
To:     Arnd Bergmann <arnd@...db.de>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Marek Vasut <marek.vasut@...il.com>
CC:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: spi-nor: stm32-quadspi: avoid unintialized return
 code

hi Arnd

thx Arnd for compilation warning (gcc <= 4.6)

Acked-by: Ludovic Barre <ludovic.barre@...com>

PS: at runtime stm32_qspi_tx_poll can't be call,
because stm32_qspi_tx check if there is tx data available
	if (!cmd->tx_data)
		return 0;

BR
Ludo

On 09/14/2017 01:06 PM, Arnd Bergmann wrote:
> If we send zero-length data to stm32_qspi_tx_poll() on older
> compiler versions such as gcc-4.6, we get warned that the
> return code is uninitialized:
> 
> drivers/mtd/spi-nor/stm32-quadspi.c:248:2: error: ‘ret’ may be used uninitialized in this function [-Werror=uninitialized]
> 
> On newer compiler versions, the return code is always zero
> in this case, as the local variable gets optimized away and
> is assumed to be zero after the loop completes without error.
> 
> This changes the function to instead return -EINVAL if it
> ever gets called with a zero length buffer.
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   drivers/mtd/spi-nor/stm32-quadspi.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c b/drivers/mtd/spi-nor/stm32-quadspi.c
> index 86c0931543c5..711cfe7aa4bf 100644
> --- a/drivers/mtd/spi-nor/stm32-quadspi.c
> +++ b/drivers/mtd/spi-nor/stm32-quadspi.c
> @@ -227,7 +227,7 @@ static int stm32_qspi_tx_poll(struct stm32_qspi *qspi,
>   	void (*tx_fifo)(u8 *, void __iomem *);
>   	u32 len = cmd->len, sr;
>   	u8 *buf = cmd->buf;
> -	int ret;
> +	int ret = -EINVAL;
>   
>   	if (cmd->qspimode == CCR_FMODE_INDW)
>   		tx_fifo = stm32_qspi_write_fifo;
>