linux-kernel - Re: [PATCH v10 1/2] Added Digiteq Automotive MGB4 driver

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Message-ID: <e6a0eda7-cd54-403f-9d7b-2445c89162fc@xs4all.nl>
Date:   Fri, 22 Sep 2023 09:54:52 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     tumic@...see.org, Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Martin Tůma <martin.tuma@...iteqautomotive.com>
Subject: Re: [PATCH v10 1/2] Added Digiteq Automotive MGB4 driver

Hi Martin,

One more thing that I forgot to mention:

On 19/09/2023 18:59, tumic@...see.org wrote:
> From: Martin Tůma <martin.tuma@...iteqautomotive.com>
> 
> Digiteq Automotive MGB4 is a modular frame grabber PCIe card for automotive
> video interfaces. As for now, two modules - FPD-Link and GMSL - are
> available and supported by the driver. The card has two inputs and two
> outputs (FPD-Link only).
> 
> In addition to the video interfaces it also provides a trigger signal
> interface and a MTD interface for FPGA firmware upload.
> 
> Signed-off-by: Martin Tůma <martin.tuma@...iteqautomotive.com>
> ---

<snip>

> +static ssize_t video_source_store(struct device *dev,
> +				  struct device_attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	struct video_device *vdev = to_video_device(dev);
> +	struct mgb4_vout_dev *voutdev = video_get_drvdata(vdev);
> +	struct mgb4_dev *mgbdev = voutdev->mgbdev;
> +	struct mgb4_vin_dev *loopin_new = NULL, *loopin_old = NULL;
> +	unsigned long val;
> +	ssize_t ret;
> +	u32 config;
> +	int i;
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +	if (val > 3)
> +		return -EINVAL;
> +
> +	if (test_and_set_bit(0, &mgbdev->io_reconfig))
> +		return -EBUSY;

You need some documentation here on how and why io_reconfig is used, with a reference
to the queue_setup functions, and there you need a reference back to this function.

It is something unusual, and unusual code needs documentation.

> +
> +	ret = -EBUSY;
> +	for (i = 0; i < MGB4_VIN_DEVICES; i++)
> +		if (mgbdev->vin[i] && is_busy(&mgbdev->vin[i]->vdev))
> +			goto end;
> +	for (i = 0; i < MGB4_VOUT_DEVICES; i++)
> +		if (mgbdev->vout[i] && is_busy(&mgbdev->vout[i]->vdev))
> +			goto end;
> +
> +	config = mgb4_read_reg(&mgbdev->video, voutdev->config->regs.config);
> +
> +	if (((config & 0xc) >> 2) < MGB4_VIN_DEVICES)
> +		loopin_old = mgbdev->vin[(config & 0xc) >> 2];
> +	if (val < MGB4_VIN_DEVICES)
> +		loopin_new = mgbdev->vin[val];
> +	if (loopin_old && loopin_cnt(loopin_old) == 1)
> +		mgb4_mask_reg(&mgbdev->video, loopin_old->config->regs.config,
> +			      0x2, 0x0);
> +	if (loopin_new)
> +		mgb4_mask_reg(&mgbdev->video, loopin_new->config->regs.config,
> +			      0x2, 0x2);
> +
> +	if (val == voutdev->config->id + MGB4_VIN_DEVICES)
> +		mgb4_write_reg(&mgbdev->video, voutdev->config->regs.config,
> +			       config & ~(1 << 1));
> +	else
> +		mgb4_write_reg(&mgbdev->video, voutdev->config->regs.config,
> +			       config | (1U << 1));
> +
> +	mgb4_mask_reg(&mgbdev->video, voutdev->config->regs.config, 0xc,
> +		      val << 2);
> +
> +	ret = count;
> +end:
> +	clear_bit(0, &mgbdev->io_reconfig);
> +
> +	return ret;
> +}

Regards,

	Hans