linux-kernel - Re: [RFC v2 3/5] drm/dsi: Check for used channels

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Message-id: <563367F1.2060202@samsung.com>
Date:	Fri, 30 Oct 2015 13:52:01 +0100
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Archit Taneja <architt@...eaurora.org>,
	dri-devel@...ts.freedesktop.org
Cc:	linux-kernel@...r.kernel.org, airlied@...ux.ie, daniel@...ll.ch,
	treding@...dia.com, l.stach@...gutronix.de, robh@...nel.org,
	linux-arm-msm@...r.kernel.org, jani.nikula@...ux.intel.com
Subject: Re: [RFC v2 3/5] drm/dsi: Check for used channels

On 10/06/2015 11:24 AM, Archit Taneja wrote:
> We don't check whether a previously registered mipi_dsi_device under the
> same host shares the same virtual channel.
>
> Before registering, check if any of the registered devices doesn't
> already have the same virtual channel.
>
> This wasn't crucial when all the devices under a host were populated via
> DT. Now that we also support creating devices manually, we could end up
> in a situation where a driver tries to create a device with a virtual
> channel already taken by a device populated in DT.
>
> Signed-off-by: Archit Taneja <architt@...eaurora.org>
Beside few non-blcking nitpicks.

Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 46ee515..db6130a 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -123,6 +123,22 @@ static const struct device_type mipi_dsi_device_type = {
>  	.release = mipi_dsi_dev_release,
>  };
>  
> +static int __dsi_check_chan_busy(struct device *dev, void *data)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(dev);
> +	u32 reg = *(u32 *) data;
> +
> +	if (dsi && dsi->channel == reg)
Maybe simpler would be:

    u32 *reg = data;
 
    if (dsi && dsi->channel == *reg)



> +		return -EBUSY;
> +
> +	return 0;
> +}
> +
> +static int mipi_dsi_check_chan_busy(struct mipi_dsi_host *host, u32 reg)
> +{
> +	return device_for_each_child(host->dev, &reg, __dsi_check_chan_busy);
> +}
> +
>  struct mipi_dsi_device *mipi_dsi_device_new(struct mipi_dsi_host *host,
>  					    struct mipi_dsi_device_info *info)
>  {
> @@ -150,14 +166,20 @@ struct mipi_dsi_device *mipi_dsi_device_new(struct mipi_dsi_host *host,
>  
>  	dev_set_name(&dsi->dev, "%s.%d", dev_name(host->dev), info->reg);
>  
> +	r = mipi_dsi_check_chan_busy(host, info->reg);

I know this r variable was introduced in the 1st patch, but if you will send
next iteration
consider replacing it with ret, looks more readable and follows file convention :)

Regards
Andrzej

> +	if (r)
> +		goto err;
> +
>  	r = device_register(&dsi->dev);
>  	if (r) {
>  		dev_err(dev, "failed to register device: %d\n", r);
> -		kfree(dsi);
> -		return ERR_PTR(r);
> +		goto err;
>  	}
>  
>  	return dsi;
> +err:
> +	kfree(dsi);
> +	return ERR_PTR(r);
>  }
>  EXPORT_SYMBOL(mipi_dsi_device_new);
>  

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