linux-kernel - Re: [Patch v6 3/3] media: ti-vpe: Add CAL v4l2 camera capture driver

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Message-ID: <20160219145423.49aaa0b9@recife.lan>
Date:	Fri, 19 Feb 2016 14:54:23 -0200
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Benoit Parrot <bparrot@...com>
Cc:	Hans Verkuil <hverkuil@...all.nl>, <linux-media@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [Patch v6 3/3] media: ti-vpe: Add CAL v4l2 camera capture
 driver

Em Wed, 6 Jan 2016 17:37:26 -0600
Benoit Parrot <bparrot@...com> escreveu:

> The Camera Adaptation Layer (CAL) is a block which consists of a dual
> port CSI2/MIPI camera capture engine.
> Port #0 can handle CSI2 camera connected to up to 4 data lanes.
> Port #1 can handle CSI2 camera connected to up to 2 data lanes.
> The driver implements the required API/ioctls to be V4L2 compliant.
> Driver supports the following:
>     - V4L2 API using DMABUF/MMAP buffer access based on videobuf2 api
>     - Asynchronous sensor sub device registration
>     - DT support
> 
> Signed-off-by: Benoit Parrot <bparrot@...com>
> Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
> ---

...

> +/* timeperframe is arbitrary and continuous */
> +static int cal_enum_frameintervals(struct file *file, void *priv,
> +				   struct v4l2_frmivalenum *fival)
> +{
> +	struct cal_ctx *ctx = video_drvdata(file);
> +	const struct cal_fmt *fmt;
> +	struct v4l2_subdev_frame_size_enum fse;
> +	int ret;
> +
> +	if (fival->index)
> +		return -EINVAL;
> +
> +	fmt = find_format_by_pix(ctx, fival->pixel_format);
> +	if (!fmt)
> +		return -EINVAL;
> +
> +	/* check for valid width/height */
> +	ret = 0;
> +	fse.pad = 0;
> +	fse.code = fmt->code;
> +	fse.which = V4L2_SUBDEV_FORMAT_ACTIVE;
> +	for (fse.index = 0; ; fse.index++) {
> +		ret = v4l2_subdev_call(ctx->sensor, pad, enum_frame_size,
> +				       NULL, &fse);
> +		if (ret)
> +			return -EINVAL;
> +
> +		if ((fival->width == fse.max_width) &&
> +		    (fival->height == fse.max_height))
> +			break;
> +		else if ((fival->width >= fse.min_width) &&
> +			 (fival->width <= fse.max_width) &&
> +			 (fival->height >= fse.min_height) &&
> +			 (fival->height <= fse.max_height))
> +			break;
> +
> +		return -EINVAL;
> +	}
> +
> +	fival->type = V4L2_FRMIVAL_TYPE_DISCRETE;
> +	fival->discrete.numerator = 1;
> +	fival->discrete.denominator = 30;
> +
> +	return 0;
> +}

The above routine is too complex and sounds wrong. Why do you
need a loop there, if the loop will either return -EINVAL or
be aborted the first time it runs?

The way it is, it is just confusing and produces a smatch error:

	drivers/media/platform/ti-vpe/cal.c:1219 cal_enum_frameintervals() info: ignoring unreachable code.

If all you want here is to run the loop once, this patch would do the
same, with a clearer logic.

ti-vpe/cal: Simplify the logic to avoid confusing smatch

drivers/media/platform/ti-vpe/cal.c:1219 cal_enum_frameintervals() info: ignoring unreachable code.

This is caused by a very confusing logic that looks like a loop, but
it runs only once.

Signed-off-by: Mauro Carvalho Chehab <mchehab@....samsung.com>

diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
index 35fa1071c5b2..62721ee7b9bc 100644
--- a/drivers/media/platform/ti-vpe/cal.c
+++ b/drivers/media/platform/ti-vpe/cal.c
@@ -1216,29 +1216,28 @@ static int cal_enum_frameintervals(struct file *file, void *priv,
 	fse.pad = 0;
 	fse.code = fmt->code;
 	fse.which = V4L2_SUBDEV_FORMAT_ACTIVE;
-	for (fse.index = 0; ; fse.index++) {
-		ret = v4l2_subdev_call(ctx->sensor, pad, enum_frame_size,
-				       NULL, &fse);
-		if (ret)
-			return -EINVAL;
-
-		if ((fival->width == fse.max_width) &&
-		    (fival->height == fse.max_height))
-			break;
-		else if ((fival->width >= fse.min_width) &&
-			 (fival->width <= fse.max_width) &&
-			 (fival->height >= fse.min_height) &&
-			 (fival->height <= fse.max_height))
-			break;
+	fse.index = 0;
 
+	ret = v4l2_subdev_call(ctx->sensor, pad, enum_frame_size,
+			       NULL, &fse);
+	if (ret)
 		return -EINVAL;
-	}
 
 	fival->type = V4L2_FRMIVAL_TYPE_DISCRETE;
 	fival->discrete.numerator = 1;
 	fival->discrete.denominator = 30;
 
-	return 0;
+	if ((fival->width == fse.max_width) &&
+	    (fival->height == fse.max_height))
+		return 0;
+
+	if ((fival->width >= fse.min_width) &&
+	    (fival->width <= fse.max_width) &&
+	    (fival->height >= fse.min_height) &&
+	    (fival->height <= fse.max_height))
+		return 0;
+
+	return -EINVAL;
 }
 
 /*