linux-kernel - Re: [PATCH v2.1 1/3] v4l: common: v4l2_get_link

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Date:   Sun, 21 Feb 2021 20:56:11 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Andrey Konovalov <andrey.konovalov@...aro.org>
Cc:     junak.pub@...il.com, robert.foss@...aro.org,
        sakari.ailus@...ux.intel.com, todor.too@...il.com,
        agross@...nel.org, bjorn.andersson@...aro.org, mchehab@...nel.org,
        jacopo@...ndi.org, linux-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2.1 1/3] v4l: common: v4l2_get_link_freq: add printing a
 warning

Hi Andrey,

Thank you for the patch.

On Thu, Feb 18, 2021 at 08:16:40PM +0300, Andrey Konovalov wrote:
> Print a warning if V4L2_CID_LINK_FREQ control is not implemented.
> 
> Signed-off-by: Andrey Konovalov <andrey.konovalov@...aro.org>
> Reviewed-by: Jacopo Mondi <jacopo@...ndi.org>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/media/v4l2-core/v4l2-common.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 133d20e40f82..04af03285a20 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -469,6 +469,11 @@ s64 v4l2_get_link_freq(struct v4l2_ctrl_handler *handler, unsigned int mul,
>  			return -ENOENT;
>  
>  		freq = div_u64(v4l2_ctrl_g_ctrl_int64(ctrl) * mul, div);
> +
> +		pr_warn("%s: Link frequency estimated using pixel rate: result might be inaccurate\n",
> +			__func__);
> +		pr_warn("%s: Consider implementing support for V4L2_CID_LINK_FREQ in the transmitter driver\n",
> +			__func__);

It would still be nice if v4l2_ctrl_handler was extended with a struct
device pointer to use dev_warn() here, and allow replacing "the
transmitter driver" with the driver name.

>  	}
>  
>  	return freq > 0 ? freq : -EINVAL;

-- 
Regards,

Laurent Pinchart