Re: [PATCH 21/23] gpio: mockup: provide a way to delete dummy chips

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Fri, Sep 04, 2020 at 05:45:45PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> 
> Add a new debugfs attribute 'delete_device' to which the chip label can
> be written to dynamically remove the associated dummy device.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> ---
>  drivers/gpio/gpio-mockup.c | 70 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 69 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> index 1353239dc315..9d2de78a45c2 100644
> --- a/drivers/gpio/gpio-mockup.c
> +++ b/drivers/gpio/gpio-mockup.c
> @@ -19,6 +19,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/property.h>
>  #include <linux/slab.h>
> +#include <linux/string.h>
>  #include <linux/string_helpers.h>
>  #include <linux/uaccess.h>
>  
> @@ -668,14 +669,81 @@ static int __init gpio_mockup_register_chips_from_params(void)
>  	return 0;
>  }
>  
> -static int __init gpio_mockup_init(void)
> +static ssize_t gpio_mockup_debugfs_delete_device_write(struct file *file,
> +						const char __user *usr_buf,
> +						size_t size, loff_t *ppos)
>  {
> +	struct gpio_mockup_device *mockup_dev;
> +	char label[GPIO_MOCKUP_LABEL_SIZE];
> +	struct list_head *curr;
> +	struct device *dev;
> +	const char *prop;
>  	int ret;
>  
> +	if (*ppos != 0)
> +		return -EINVAL;
> +
> +	ret = getline_from_user(label, sizeof(label), usr_buf, size);
> +	if (ret < 0)
> +		return ret;
> +
> +	mutex_lock(&gpio_mockup_devices_lock);
> +
> +	list_for_each(curr, &gpio_mockup_devices) {
> +		mockup_dev = list_entry(curr, struct gpio_mockup_device, list);

Why not list_for_each_entry()?

> +		dev = &mockup_dev->pdev->dev;
> +
> +		ret = device_property_read_string(dev, "chip-label", &prop);
> +		if (ret) {
> +			mutex_unlock(&gpio_mockup_devices_lock);
> +			return ret;
> +		}
> +
> +		if (sysfs_streq(label, prop)) {
> +			gpio_mockup_unregister_one_device(mockup_dev);
> +			mutex_unlock(&gpio_mockup_devices_lock);
> +			return size;
> +		}
> +	}
> +
> +	mutex_unlock(&gpio_mockup_devices_lock);
> +	return -ENODEV;
> +}
> +
> +static const struct file_operations gpio_mockup_debugfs_delete_device_ops = {
> +	.owner = THIS_MODULE,
> +	.open = gpio_mockup_debugfs_open,
> +	.write = gpio_mockup_debugfs_delete_device_write,
> +	.llseek = no_llseek,
> +	.release = single_release,
> +};
> +
> +static int __init gpio_mockup_debugfs_init(void)
> +{
> +	struct dentry *entry;
> +
>  	gpio_mockup_dbg_dir = debugfs_create_dir("gpio-mockup", NULL);
>  	if (IS_ERR(gpio_mockup_dbg_dir))
>  		return PTR_ERR(gpio_mockup_dbg_dir);
>  
> +	entry = debugfs_create_file("delete_device", 0200, gpio_mockup_dbg_dir,
> +				NULL, &gpio_mockup_debugfs_delete_device_ops);
> +	if (IS_ERR(entry)) {
> +		debugfs_remove_recursive(gpio_mockup_dbg_dir);
> +		return PTR_ERR(entry);
> +	}
> +
> +	return 0;
> +}
> +
> +static int __init gpio_mockup_init(void)
> +{
> +	int ret;
> +
> +	ret = gpio_mockup_debugfs_init();
> +	if (ret)
> +		return ret;
> +
>  	ret = platform_driver_register(&gpio_mockup_driver);
>  	if (ret) {
>  		pr_err("error registering platform driver\n");
> -- 
> 2.26.1
> 

-- 
With Best Regards,
Andy Shevchenko