[PATCH v9 2/2] video: drm: exynos: Add pinctrl support to fimd

[PATCH v9 2/2] video: drm: exynos: Add pinctrl support to fimd

[Sylwester Nawrocki]

On 02/28/2013 05:12 AM, Vikas Sajjan wrote:
> Adds support for pinctrl to drm fimd
>
> Signed-off-by: Leela Krishna Amudala<l.krishna@samsung.com>
> Signed-off-by: Vikas Sajjan<vikas.sajjan@linaro.org>
> ---
>   drivers/gpu/drm/exynos/exynos_drm_fimd.c |    9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> index e323cf9..21ada8d 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> @@ -19,6 +19,7 @@
>   #include<linux/clk.h>
>   #include<linux/of_device.h>
>   #include<linux/pm_runtime.h>
> +#include<linux/pinctrl/consumer.h>
>
>   #include<video/of_display_timing.h>
>   #include<video/samsung_fimd.h>
> @@ -879,6 +880,7 @@ static int fimd_probe(struct platform_device *pdev)
>   	struct exynos_drm_fimd_pdata *pdata;
>   	struct exynos_drm_panel_info *panel;
>   	struct resource *res;
> +	struct pinctrl *pctrl;
>   	int win;
>   	int ret = -EINVAL;
>
> @@ -897,6 +899,13 @@ static int fimd_probe(struct platform_device *pdev)
>   			DRM_ERROR("failed: of_get_fb_videomode() : %d\n", ret);
>   			return ret;
>   		}
> +		pctrl = devm_pinctrl_get_select_default(dev);
> +		if (IS_ERR_OR_NULL(pctrl)) {
> +			DRM_ERROR("failed: devm_pinctrl_get_select_default():"
> +				"%d\n", PTR_RET(pctrl));
> +			return PTR_ERR(pctrl);

In situations like this I really side attempts to remove IS_ERR_OR_NULL()
macro from the kernel completely ([1], [2]). What is the value returned 
from
fimd_probe() when devm_pinctrl_get_select_default() returns NULL ?

What header file have you added to use struct pinctrl in this driver ?
Is this data structure fully declared there ? Are drivers supposed to
dereference struct pinctrl at all ?

I believe original intention was to have the pinctrl handle as an opaque
cookie, and as long as it is used with the pinctrl API only and tested
for errors with *IS_ERR()*, everything should be fine. The pinctrl API
should handle any NULL pointer as it returned it to a driver in the first
place.

Please just use IS_ERR(), let's stop this IS_ERR_OR_NULL() insanity.

> +		}
> +
>   	} else {
>   		pdata = pdev->dev.platform_data;
>   		if (!pdata) {

[1] 
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-January/140543.html
[2] http://www.mail-archive.com/linux-omap at vger.kernel.org/msg78030.html

[PATCH v9 2/2] video: drm: exynos: Add pinctrl support to fimd

[Russell King - ARM Linux]

On Thu, Feb 28, 2013 at 11:03:57PM +0100, Sylwester Nawrocki wrote:
> Please just use IS_ERR(), let's stop this IS_ERR_OR_NULL() insanity.

Yes, indeed.

On that topic (and off-topic for this thread, sorry) I've committed
a set of patches to remove most users of IS_ERR_OR_NULL() from arch/arm.
These are the last remaining ones there - and I don't want to see any
more appearing:

arch/arm/plat-samsung/clock.c:	if (IS_ERR_OR_NULL(clk))
arch/arm/plat-samsung/clock.c:	if (!IS_ERR_OR_NULL(clk) && clk->ops && clk->ops->round_rate)
arch/arm/plat-samsung/clock.c:	if (IS_ERR_OR_NULL(clk))
arch/arm/plat-samsung/clock.c:	if (IS_ERR_OR_NULL(clk) || IS_ERR_OR_NULL(parent))
arch/arm/mach-imx/devices/platform-ipu-core.c:	if (IS_ERR_OR_NULL(imx_ipu_coredev))
arch/arm/mach-imx/devices/platform-ipu-core.c:	if (IS_ERR_OR_NULL(imx_ipu_coredev))
arch/arm/kernel/smp_twd.c:		 * We use IS_ERR_OR_NULL() here, because if the clock stubs
arch/arm/kernel/smp_twd.c:		if (!IS_ERR_OR_NULL(twd_clk))

They currently all legal uses of it - though I'm sure that the samsung
clock uses can be reduced to just IS_ERR().  The IMX use looks "valid"
in that imx_ipu_coredev really can be an error pointer (on failure) or
NULL if the platform device hasn't yet been created.  The TWD one is
explained in the comments in the code (if people had to write explanations
for using IS_ERR_OR_NULL(), we'd probably have it used correctly!)