Re: [REVIEW PATCH 1/5] v4l2: add const to argument of write-only s_frequency ioctl.

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

Thanks for the patch.

On Friday 15 March 2013 11:27:21 Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> This ioctl is defined as IOW, so pass the argument as const.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

[snip]

> diff --git a/drivers/media/radio/radio-isa.c
> b/drivers/media/radio/radio-isa.c index fe0a4f8..0c1e27b 100644
> --- a/drivers/media/radio/radio-isa.c
> +++ b/drivers/media/radio/radio-isa.c
> @@ -102,17 +102,18 @@ static int radio_isa_s_tuner(struct file *file, void
> *priv, }
> 
>  static int radio_isa_s_frequency(struct file *file, void *priv,
> -				struct v4l2_frequency *f)
> +				const struct v4l2_frequency *f)
>  {
>  	struct radio_isa_card *isa = video_drvdata(file);
> +	u32 freq = f->frequency;
>  	int res;
> 
>  	if (f->tuner != 0 || f->type != V4L2_TUNER_RADIO)
>  		return -EINVAL;
> -	f->frequency = clamp(f->frequency, FREQ_LOW, FREQ_HIGH);
> -	res = isa->drv->ops->s_frequency(isa, f->frequency);
> +	freq = clamp(freq, FREQ_LOW, FREQ_HIGH);

Micro-optimization here, you could just declare

	u32 freq;

above and then write

	freq = clamp(f->frequency, FREQ_LOW, FREQ_HIGH);

> +	res = isa->drv->ops->s_frequency(isa, freq);
>  	if (res == 0)
> -		isa->freq = f->frequency;
> +		isa->freq = freq;
>  	return res;
>  }
> 
> diff --git a/drivers/media/radio/radio-keene.c
> b/drivers/media/radio/radio-keene.c index 296941a..a90b7a8 100644
> --- a/drivers/media/radio/radio-keene.c
> +++ b/drivers/media/radio/radio-keene.c
> @@ -82,9 +82,12 @@ static inline struct keene_device *to_keene_dev(struct
> v4l2_device *v4l2_dev) /* Set frequency (if non-0), PA, mute and turn
> on/off the FM transmitter. */ static int keene_cmd_main(struct keene_device
> *radio, unsigned freq, bool play) {
> -	unsigned short freq_send = freq ? (freq - 76 * 16000) / 800 : 0;
> +	unsigned short freq_send;
>  	int ret;
> 
> +	if (freq)
> +		freq = clamp(freq, FREQ_MIN * FREQ_MUL, FREQ_MAX * FREQ_MUL);

There was no similar if (freq) in the function below, doesn't this change the 
behaviour ?

> +	freq_send = freq ? (freq - 76 * 16000) / 800 : 0;
>  	radio->buffer[0] = 0x00;
>  	radio->buffer[1] = 0x50;
>  	radio->buffer[2] = (freq_send >> 8) & 0xff;
> @@ -215,14 +218,12 @@ static int vidioc_s_modulator(struct file *file, void
> *priv, }
> 
>  static int vidioc_s_frequency(struct file *file, void *priv,
> -				struct v4l2_frequency *f)
> +				const struct v4l2_frequency *f)
>  {
>  	struct keene_device *radio = video_drvdata(file);
> 
>  	if (f->tuner != 0 || f->type != V4L2_TUNER_RADIO)
>  		return -EINVAL;
> -	f->frequency = clamp(f->frequency,
> -			FREQ_MIN * FREQ_MUL, FREQ_MAX * FREQ_MUL);
>  	return keene_cmd_main(radio, f->frequency, true);
>  }
> 

[snip]

> diff --git a/drivers/media/radio/radio-miropcm20.c
> b/drivers/media/radio/radio-miropcm20.c index 3d0ff44..2b8d31d 100644
> --- a/drivers/media/radio/radio-miropcm20.c
> +++ b/drivers/media/radio/radio-miropcm20.c
> @@ -131,14 +131,14 @@ static int vidioc_g_frequency(struct file *file, void
> *priv,
> 
> 
>  static int vidioc_s_frequency(struct file *file, void *priv,
> -				struct v4l2_frequency *f)
> +				const struct v4l2_frequency *f)
>  {
>  	struct pcm20 *dev = video_drvdata(file);
> 
>  	if (f->tuner != 0 || f->type != V4L2_TUNER_RADIO)
>  		return -EINVAL;
> 
> -	dev->freq = clamp(f->frequency, 87 * 16000U, 108 * 16000U);
> +	dev->freq = clamp_t(u32, f->frequency, 87 * 16000U, 108 * 16000U);

f->frequency and the two clamp boundaries are unsigned, did clamp() throw a 
warning ?

>  	pcm20_setfreq(dev, dev->freq);
>  	return 0;
>  }

[snip]

> diff --git a/drivers/media/usb/tlg2300/pd-video.c
> b/drivers/media/usb/tlg2300/pd-video.c index dab0ca3..8ef7c8c 100644
> --- a/drivers/media/usb/tlg2300/pd-video.c
> +++ b/drivers/media/usb/tlg2300/pd-video.c
> @@ -1079,10 +1079,11 @@ static int set_frequency(struct poseidon *pd, u32
> *frequency) }
> 
>  static int vidioc_s_frequency(struct file *file, void *fh,
> -				struct v4l2_frequency *freq)
> +				const struct v4l2_frequency *freq)
>  {
>  	struct front_face *front = fh;
>  	struct poseidon *pd = front->pd;
> +	u32 frequency = freq->frequency;
> 
>  	if (freq->tuner)
>  		return -EINVAL;
> @@ -1090,7 +1091,7 @@ static int vidioc_s_frequency(struct file *file, void
> *fh, pd->pm_suspend = pm_video_suspend;
>  	pd->pm_resume = pm_video_resume;
>  #endif
> -	return set_frequency(pd, &freq->frequency);
> +	return set_frequency(pd, &frequency);

Wouldn't it be better to pass the frequency by value to set_frequency() ?

>  }
> 

[snip]

> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index b137a5e..1a82a50 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -191,7 +191,7 @@ struct v4l2_subdev_core_ops {
>   */
>  struct v4l2_subdev_tuner_ops {
>  	int (*s_radio)(struct v4l2_subdev *sd);
> -	int (*s_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);
> +	int (*s_frequency)(struct v4l2_subdev *sd, const struct v4l2_frequency
> *freq);

Ideally we shouldn't push the same design mistake to subdev ops, but that 
would require too many changes in all the drivers, so I'm fine with this.

> 	int (*g_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);
> 	int (*g_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);
>  	int (*s_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);

-- 
Regards,

Laurent Pinchart