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Date:   Thu, 18 Feb 2021 08:55:10 +0100
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Andrey Konovalov <andrey.konovalov@linaro.org>
Cc:     junak.pub@gmail.com, robert.foss@linaro.org,
        sakari.ailus@linux.intel.com, todor.too@gmail.com,
        agross@kernel.org, bjorn.andersson@linaro.org, mchehab@kernel.org,
        laurent.pinchart@ideasonboard.com, linux-media@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] v4l: common: v4l2_get_link_freq: add printing a
 warning
Message-ID: <20210218075510.dcqbpmft46bymmnd@uno.localdomain>
References: <20210217221134.2606-1-andrey.konovalov@linaro.org>
 <20210217221134.2606-2-andrey.konovalov@linaro.org>
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In-Reply-To: <20210217221134.2606-2-andrey.konovalov@linaro.org>
Precedence: bulk

Hi Andrey,

On Thu, Feb 18, 2021 at 01:11:32AM +0300, Andrey Konovalov wrote:
> Print a warning if V4L2_CID_LINK_FREQ control is not implemented.
>
> Signed-off-by: Andrey Konovalov <andrey.konovalov@linaro.org>
> ---
>  drivers/media/v4l2-core/v4l2-common.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 133d20e40f82..f1abdf2ab4ec 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -461,6 +461,8 @@ s64 v4l2_get_link_freq(struct v4l2_ctrl_handler *handler, unsigned int mul,
>
>  		freq = qm.value;
>  	} else {
> +		pr_warn("%s: V4L2_CID_LINK_FREQ not implemented\n", __func__);
> +

It's a shame we can't access a struct device * somehow :(
Also, nitpicking (please bear with me here) it is absolutely correct
that V4L2_CID_LINK_FREQ is not implemented, but I think the real deal
here is that the link rate is estimanted from PIXEL_RATE and that
might be wrong.

What about (insipired from the error message in match_fwnode() which I
find useful)

                pr_warn("%s: Link frequency estimanted 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___);

Anyway, whatever works
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

Thanks
   j

>  		if (!mul || !div)
>  			return -ENOENT;
>
> --
> 2.17.1
>