Re: [RFC PATCH v2 2/3] accel: add dedicated minor for accelerator devices

[Jiho Chu]

On Wed,  2 Nov 2022 22:34:04 +0200
Oded Gabbay <ogabbay@xxxxxxxxxx> wrote:

> +/**
> + * accel_open - open method for ACCEL file
> + * @inode: device inode
> + * @filp: file pointer.
> + *
> + * This function must be used by drivers as their &file_operations.open method.
> + * It looks up the correct ACCEL device and instantiates all the per-file
> + * resources for it. It also calls the &drm_driver.open driver callback.
> + *
> + * Return: 0 on success or negative errno value on failure.
> + */
> +int accel_open(struct inode *inode, struct file *filp)
> +{
> +	struct drm_device *dev;
> +	struct drm_minor *minor;
> +	int retcode;
> +
> +	minor = accel_minor_acquire(iminor(inode));
> +	if (IS_ERR(minor))
> +		return PTR_ERR(minor);
> +
> +	dev = minor->dev;
> +
> +	atomic_fetch_inc(&dev->open_count);
> +

Hi,
It needs to consider drm_global_mutex to access open_count.
please check doxy of open_count.


> +	/* share address_space across all char-devs of a single device */
> +	filp->f_mapping = dev->anon_inode->i_mapping;
> +
> +	retcode = drm_open_helper(filp, minor);
> +	if (retcode)
> +		goto err_undo;
> +
> +	return 0;
> +
> +err_undo:
> +	atomic_dec(&dev->open_count);
> +	accel_minor_release(minor);
> +	return retcode;
> +}
> +EXPORT_SYMBOL_GPL(accel_open);
> +
>  static int accel_stub_open(struct inode *inode, struct file *filp)
>  {
> -	DRM_DEBUG("Operation not supported");
> +	const struct file_operations *new_fops;
> +	struct drm_minor *minor;
> +	int err;
> +
> +	DRM_DEBUG("\n");

It seems useless.

Thanks.
Jiho Chu