linux-kernel - Re: [PATCH] spi: rockchip: fix warning of static check

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Message-ID: <CAD=FV=XW30AFHWmuz0xeCaGuBLE15WhXOWyJkD69O461HaPVOQ@mail.gmail.com>
Date:	Tue, 22 Mar 2016 09:23:27 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Mark Brown <broonie@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-spi@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH] spi: rockchip: fix warning of static check

Hi,

On Tue, Mar 22, 2016 at 4:36 AM, Shawn Lin <shawn.lin@...k-chips.com> wrote:
> Let's improve the check with -EPROBE_DEFER, otherwise
> we may pass on null pointer to PTR_ERR. That causes the
> static checker warning: passing zero to 'PTR_ERR'.
>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Cc: Doug Anderson <dianders@...omium.org>
> Cc: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
> ---
>
>  drivers/spi/spi-rockchip.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
> index bfeb0d4..2cb36d9 100644
> --- a/drivers/spi/spi-rockchip.c
> +++ b/drivers/spi/spi-rockchip.c
> @@ -726,20 +726,24 @@ static int rockchip_spi_probe(struct platform_device *pdev)
>         rs->dma_tx.ch = dma_request_slave_channel(rs->dev, "tx");

Please change from:
  dma_request_slave_channel()
to:
  dma_request_chan()

The first will never return -EPROBE_DEFER.  The second will.

>         if (IS_ERR_OR_NULL(rs->dma_tx.ch)) {

Once you've changed to dma_request_chan(), change IS_ERR_OR_NULL() to
just IS_ERR().  dma_request_chan() never returns NULL.

>                 /* Check tx to see if we need defer probing driver */
> -               if (PTR_ERR(rs->dma_tx.ch) == -EPROBE_DEFER) {
> +               if (rs->dma_tx.ch == ERR_PTR(-EPROBE_DEFER)) {

Once you've changed to use dma_request_chan(), no need to change this
line.  Leave it as it was.

>                         ret = -EPROBE_DEFER;
>                         goto err_get_fifo_len;
>                 }
>                 dev_warn(rs->dev, "Failed to request TX DMA channel\n");
> +               rs->dma_tx.ch = NULL;
>         }
>
>         rs->dma_rx.ch = dma_request_slave_channel(rs->dev, "rx");
> -       if (!rs->dma_rx.ch) {
> -               if (rs->dma_tx.ch) {
> +       if (IS_ERR_OR_NULL(rs->dma_rx.ch)) {
> +               if (rs->dma_tx.ch == ERR_PTR(-EPROBE_DEFER)) {
>                         dma_release_channel(rs->dma_tx.ch);
>                         rs->dma_tx.ch = NULL;
> +                       ret = -EPROBE_DEFER;
> +                       goto err_get_fifo_len;
>                 }
>                 dev_warn(rs->dev, "Failed to request RX DMA channel\n");
> +               rs->dma_rx.ch = NULL;

Same comments apply to the rx path.