linux-kernel - Re: [Patch v5 1/2] media: v4l: ti-vpe: Add CAL v4l2 camera capture driver

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Message-ID: <566ED532.6060308@xs4all.nl>
Date:	Mon, 14 Dec 2015 15:41:54 +0100
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Benoit Parrot <bparrot@...com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>
Cc:	linux-media@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [Patch v5 1/2] media: v4l: ti-vpe: Add CAL v4l2 camera capture
 driver

On 12/11/2015 11:16 PM, Benoit Parrot wrote:
> Mauro Carvalho Chehab <mchehab@....samsung.com> wrote on Thu [2015-Dec-03 11:19:22 -0200]:
>>> +static int cal_enum_framesizes(struct file *file, void *fh,
>>> +			       struct v4l2_frmsizeenum *fsize)
>>> +{
>>> +	struct cal_ctx *ctx = video_drvdata(file);
>>> +	const struct cal_fmt *fmt;
>>> +	struct v4l2_subdev_frame_size_enum fse;
>>> +	int ret;
>>> +
>>> +	ctx_dbg(2, ctx, "%s\n", __func__);
>>
>> This s a general note: do you really need tracing-like debug macros
>> all around the code?
>>
>> You could easily check if the functions are called via trace.
> 
> True but that also mean to rebuild the kernel in order to
> get to it since function tracing is usually not enabled
> by default.
> 

You can enable debugging by doing:

echo 2 >/sys/class/video4linux/video0/dev_debug

See also: Documentation/video4linux/v4l2-framework.txt, section "video device
debugging" for more info.

That's always available and basically does what you want.

Regards,

	Hans

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