Re: pxa2xx_spi: spi_bfin5xx: limit reaches -1 rather than 0

David Brownell
2009-02-08T16:07:39Z

On Sunday 08 February 2009, Roel Kluin wrote:
> vi drivers/spi/pxa2xx_spi.c +919
> vi drivers/spi/spi_bfin5xx.c +645
>
> if (flush(drv_data) == 0) {
> dev_err(&drv_data->pdev->dev, "pump_transfers: flush failed\n");
> message->status = -EIO;
> giveback(drv_data);
> return;
> }
>
> But with a postfix decrement limit reaches -1 rather than 0.
>
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>

Acked-by: David Brownell <dbrownell@users.sourceforge.net>

Although, note that if the *actual* count mattered here,
the correect patch would be to test "flush() < 0)" ...
except when using a "do {...} while (--limit)" idiom.

Try the thought experiment of starting with "limit = 1";
not all of these patches of your would go through the
loop even once. Fortunately in all these cases, the
limit is an arbitrary "don't loop forever" thing.

> ---
> drivers/spi/pxa2xx_spi.c | 2 +-
> drivers/spi/spi_bfin5xx.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
> index d0fc4ca..3164741 100644
> --- a/drivers/spi/pxa2xx_spi.c
> +++ b/drivers/spi/pxa2xx_spi.c
> @@ -185,7 +185,7 @@ static int flush(struct driver_data *drv_data)
> while (read_SSSR(reg) & SSSR_RNE) {
> read_SSDR(reg);
> }
> - } while ((read_SSSR(reg) & SSSR_BSY) && limit--);
> + } while ((read_SSSR(reg) & SSSR_BSY) && --limit);
> write_SSSR(SSSR_ROR, reg);
>
> return limit;
> diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
> index 7fea3cf..ea94567 100644
> --- a/drivers/spi/spi_bfin5xx.c
> +++ b/drivers/spi/spi_bfin5xx.c
> @@ -162,7 +162,7 @@ static int flush(struct driver_data *drv_data)
> unsigned long limit = loops_per_jiffy << 1;
>
> /* wait for stop and clear stat */
> - while (!(read_STAT(drv_data) & BIT_STAT_SPIF) && limit--)
> + while (!(read_STAT(drv_data) & BIT_STAT_SPIF) && --limit)
> cpu_relax();
>
> write_STAT(drv_data, BIT_STAT_CLR);
>
>