linux-kernel - Re: [PATCH] drm/msm: Move call to PTR_ERR_OR

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Date:	Thu, 28 Apr 2016 13:53:01 +0100
From:	Eric Engestrom <eric.engestrom@...tec.com>
To:	Vaishali Thakkar <vaishali.thakkar@...cle.com>
CC:	<airlied@...ux.ie>, <linux-kernel@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/msm: Move call to PTR_ERR_OR_ZERO after reassignment

On Wed, Apr 27, 2016 at 04:51:37PM +0530, Vaishali Thakkar wrote:
> Here, a location is reset to NULL before being passed to PTR_ERR.
> So, PTR_ERR should be called before its argument is reassigned
> to NULL. Further to simplify things use PTR_ERR_OR_ZERO instead
> of PTR_ERR and IS_ERR.
> 
> Problem found using Coccinelle.
> 
> Signed-off-by: Vaishali Thakkar <vaishali.thakkar@...cle.com>
> ---
>  drivers/gpu/drm/msm/edp/edp_ctrl.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/edp/edp_ctrl.c b/drivers/gpu/drm/msm/edp/edp_ctrl.c
> index 81200e9..7816541 100644
> --- a/drivers/gpu/drm/msm/edp/edp_ctrl.c
> +++ b/drivers/gpu/drm/msm/edp/edp_ctrl.c
> @@ -302,21 +302,23 @@ static void edp_clk_disable(struct edp_ctrl *ctrl, u32 clk_mask)
>  static int edp_regulator_init(struct edp_ctrl *ctrl)
>  {
>  	struct device *dev = &ctrl->pdev->dev;
> +	int ret;
>  
>  	DBG("");
>  	ctrl->vdda_vreg = devm_regulator_get(dev, "vdda");
> -	if (IS_ERR(ctrl->vdda_vreg)) {
> +	ret = PTR_ERR_OR_ZERO(ctrl->vdda_vreg);
> +	if (ret) {
>  		pr_err("%s: Could not get vdda reg, ret = %ld\n", __func__,
> -				PTR_ERR(ctrl->vdda_vreg));
> +				ret);
>  		ctrl->vdda_vreg = NULL;
> -		return PTR_ERR(ctrl->vdda_vreg);
> +		return ret;
>  	}
>  	ctrl->lvl_vreg = devm_regulator_get(dev, "lvl-vdd");
> -	if (IS_ERR(ctrl->lvl_vreg)) {
> -		pr_err("Could not get lvl-vdd reg, %ld",
> -				PTR_ERR(ctrl->lvl_vreg));
> +	ret = PTR_ERR_OR_ZERO(ctrl->lvl_vreg);
> +	if (ret) {

While you're rewriting them, it might be worth making these two pr_err()
print the same format, e.g.:

	pr_err("%s: Could not get lvl-vdd reg, ret = %ld\n", __func__, ret);

> +		pr_err("Could not get lvl-vdd reg, %ld", ret);
>  		ctrl->lvl_vreg = NULL;
> -		return PTR_ERR(ctrl->lvl_vreg);
> +		return ret;
>  	}
>  
>  	return 0;
> -- 
> 2.1.4

Reviewed-by: Eric Engestrom <eric.engestrom@...tec.com>