linux-kernel - Re: [PATCH v1 1/2] soc: qcom: rmtfs-mem: Add class to enable uevents

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Message-ID: <20181221011853.GA189656@google.com>
Date:   Thu, 20 Dec 2018 17:18:54 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ben Chan <benchan@...omium.org>, linux-arm-msm@...r.kernel.org,
        David Brown <david.brown@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] soc: qcom: rmtfs-mem: Add class to enable uevents

Hi Evan,

On Mon, Dec 17, 2018 at 04:08:33PM -0800, Evan Green wrote:
> Currently the qcom_rmtfs_memN devices are entirely invisible to the udev world.
> Add a class to the rmtfs device so that uevents fire when the device is added.
> 
> Signed-off-by: Evan Green <evgreen@...omium.org>
> ---
> 
>  drivers/soc/qcom/rmtfs_mem.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c
> index 97bb5989aa211..0bf800ee2a978 100644
> --- a/drivers/soc/qcom/rmtfs_mem.c
> +++ b/drivers/soc/qcom/rmtfs_mem.c
> @@ -132,6 +132,11 @@ static int qcom_rmtfs_mem_release(struct inode *inode, struct file *filp)
>  	return 0;
>  }
>  
> +static struct class rmtfs_class = {
> +	.owner          = THIS_MODULE,
> +	.name           = "rmtfs",
> +};
> +
>  static const struct file_operations qcom_rmtfs_mem_fops = {
>  	.owner = THIS_MODULE,
>  	.open = qcom_rmtfs_mem_open,
> @@ -173,9 +178,15 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>  
>  	}
>  
> +	ret  = class_register(&rmtfs_class);
> +	if (ret)
> +		return ret;

Hmm, is this how classes are supposed to work? Usually, you have the
possibility of more than 1 device per class, and therefore you don't
register the class in the driver probe -- you register it in the init()
routine, or something similar. As it is, I expect this will break if
there were ever a second rmtfs device.

Brian

> +
>  	rmtfs_mem = kzalloc(sizeof(*rmtfs_mem), GFP_KERNEL);
> -	if (!rmtfs_mem)
> -		return -ENOMEM;
> +	if (!rmtfs_mem) {
> +		ret = -ENOMEM;
> +		goto unregister_class;
> +	}
>  
>  	rmtfs_mem->addr = rmem->base;
>  	rmtfs_mem->client_id = client_id;
> @@ -199,8 +210,8 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>  
>  	dev_set_name(&rmtfs_mem->dev, "qcom_rmtfs_mem%d", client_id);
>  	rmtfs_mem->dev.id = client_id;
> +	rmtfs_mem->dev.class = &rmtfs_class;
>  	rmtfs_mem->dev.devt = MKDEV(MAJOR(qcom_rmtfs_mem_major), client_id);
> -
>  	ret = cdev_device_add(&rmtfs_mem->cdev, &rmtfs_mem->dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "failed to add cdev: %d\n", ret);
> @@ -235,11 +246,13 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev)
>  
>  	return 0;
>  
> +
>  remove_cdev:
>  	cdev_device_del(&rmtfs_mem->cdev, &rmtfs_mem->dev);
>  put_device:
>  	put_device(&rmtfs_mem->dev);
> -
> +unregister_class:
> +	class_unregister(&rmtfs_class);
>  	return ret;
>  }
>  
> @@ -258,7 +271,7 @@ static int qcom_rmtfs_mem_remove(struct platform_device *pdev)
>  
>  	cdev_device_del(&rmtfs_mem->cdev, &rmtfs_mem->dev);
>  	put_device(&rmtfs_mem->dev);
> -
> +	class_unregister(&rmtfs_class);
>  	return 0;
>  }
>  
> -- 
> 2.18.1
>