Re: [PATCH] mtd: spi-nor: stm32-quadspi: Fix uninitialized error return code

[Ludovic BARRE]

On 07/17/2017 12:22 PM, Geert Uytterhoeven wrote:
> Hi Ludovic,
>
> On Mon, Jul 17, 2017 at 11:56 AM, Ludovic BARRE <ludovic.barre@xxxxxx> wrote:
> > Today only write_reg could be call with len=0 (spi-nor.c:
> > write_enable/disable, set_4byte, erase_chip)
> >
> > But your remark make sense to prevent: gcc warning and framework evolution
> > ...
> >
> >
> > -In stm32-quadspi.c transfer data is enabled if tx_data is true (some
> > actions under this bool)
> >
> > stm32_qspi_write_reg has already this protection with "!!(buf && len > 0);"
> >
> > but we could extend this protection
> >
> > -    cmd.tx_data = true;
> > +    cmd.tx_data = !!(len > 0);
> >
> > In : stm32_qspi_read, stm32_qspi_write, stm32_qspi_read_reg
>
> Ah, I missed the check for !cmd->tx_data at the top of stm32_qspi_tx()
>
> > -And to avoid gcc warning: I prefer initialize "ret" in the beginning of
> > function
> >
> > -    int ret;
> > +    int ret = 0;
> >
> > I tested this changes, and it's ok for me.
> >
> > Geert could you resend a new version, or do you prefer that I take care of
> > it
>
> If you initialized ret at the beginning, you lose the ability to catch newly
> introduced similar bugs in the future.
like discuss in thread https://patchwork.kernel.org/patch/9952849/ with 
Arnd and Geert

Cyrille, Marek: could you take geert patch and abandon
https://patchwork.kernel.org/patch/9952849/
thanks

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

> > On 07/15/2017 10:00 AM, Geert Uytterhoeven wrote:
> > > With gcc 4.1.2:
> > >
> > >       drivers/mtd/spi-nor/stm32-quadspi.c: In function
> > > âstm32_qspi_tx_pollâ:
> > >       drivers/mtd/spi-nor/stm32-quadspi.c:230: warning: âretâ may be used
> > > uninitialized in this function
> > >
> > > Indeed, if stm32_qspi_cmd.len is zero, ret will be uninitialized.
> > > This length is passed from outside the driver using the
> > > spi_nor.{read,write}{,_reg}() callbacks.
> > >
> > > Several functions in drivers/mtd/spi-nor/spi-nor.c (e.g. write_enable(),
> > > write_disable(), and erase_chip()) call spi_nor.write_reg() with a zero
> > > length.
> > >
> > > Fix this by returning an explicit zero on success.
> > >
> > > Fixes: 0d43d7ab277a048c ("mtd: spi-nor: add driver for STM32 quad spi
> > > flash controller")
> > > Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > > ---
> > >    drivers/mtd/spi-nor/stm32-quadspi.c | 4 ++--
> > >    1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c
> > > b/drivers/mtd/spi-nor/stm32-quadspi.c
> > > index 86c0931543c538c3..ad6a3e1844cbe5ec 100644
> > > --- a/drivers/mtd/spi-nor/stm32-quadspi.c
> > > +++ b/drivers/mtd/spi-nor/stm32-quadspi.c
> > > @@ -240,12 +240,12 @@ static int stm32_qspi_tx_poll(struct stm32_qspi
> > > *qspi,
> > >
> > > STM32_QSPI_FIFO_TIMEOUT_US);
> > >                  if (ret) {
> > >                          dev_err(qspi->dev, "fifo timeout (stat:%#x)\n",
> > > sr);
> > > -                       break;
> > > +                       return ret;
> > >                  }
> > >                  tx_fifo(buf++, qspi->io_base + QUADSPI_DR);
> > >          }
> > >    -     return ret;
> > > +       return 0;
> > >    }
> > >      static int stm32_qspi_tx_mm(struct stm32_qspi *qspi,
>
> Gr{oetje,eeting}s,
>
>                          Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds