linux-kernel - Re: [PATCH v5 2/2] staging: ion: create one device entry per heap

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Date:   Wed, 18 Oct 2017 13:07:33 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        sumit.semwal@...aro.org, gregkh@...uxfoundation.org,
        arve@...roid.com, riandrews@...roid.com, broonie@...nel.org,
        dan.carpenter@...cle.com
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v5 2/2] staging: ion: create one device entry per heap

On 09/27/2017 06:20 AM, Benjamin Gaignard wrote:
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 93e2c90..092b24c 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -40,6 +40,8 @@
>  
>  #include "ion.h"
>  
> +#define ION_DEV_MAX 32
> +
>  static struct ion_device *internal_dev;
>  static int heap_id;
>  
> @@ -537,15 +539,28 @@ static int debug_shrink_get(void *data, u64 *val)
>  DEFINE_SIMPLE_ATTRIBUTE(debug_shrink_fops, debug_shrink_get,
>  			debug_shrink_set, "%llu\n");
>  
> -void ion_device_add_heap(struct ion_heap *heap)
> +int ion_device_add_heap(struct ion_heap *heap)
>  {
>  	struct dentry *debug_file;
>  	struct ion_device *dev = internal_dev;
> +	int ret = 0;
>  
>  	if (!heap->ops->allocate || !heap->ops->free)
>  		pr_err("%s: can not add heap with invalid ops struct.\n",
>  		       __func__);
>  
> +	if (heap_id >= ION_DEV_MAX)
> +		return -EBUSY;
> +
> +	heap->ddev.devt = MKDEV(MAJOR(dev->devt), heap_id);
> +	dev_set_name(&heap->ddev, "ion%d", heap_id);
> +	device_initialize(&heap->ddev);
> +	cdev_init(&heap->chrdev, &ion_fops);
> +	heap->chrdev.owner = THIS_MODULE;
> +	ret = cdev_device_add(&heap->chrdev, &heap->ddev);
> +	if (ret < 0)
> +		return ret;
> +
>  	spin_lock_init(&heap->free_lock);
>  	heap->free_list_size = 0;
>  
> @@ -583,6 +598,8 @@ void ion_device_add_heap(struct ion_heap *heap)
>  
>  	dev->heap_cnt++;
>  	up_write(&dev->lock);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(ion_device_add_heap);
>  
> @@ -595,6 +612,7 @@ static int ion_device_create(void)
>  	if (!idev)
>  		return -ENOMEM;
>  
> +#ifdef CONFIG_ION_LEGACY_DEVICE_API
>  	idev->dev.minor = MISC_DYNAMIC_MINOR;
>  	idev->dev.name = "ion";
>  	idev->dev.fops = &ion_fops;
> @@ -605,6 +623,17 @@ static int ion_device_create(void)
>  		kfree(idev);
>  		return ret;
>  	}
> +#endif
> +
> +	ret = alloc_chrdev_region(&idev->devt, 0, ION_DEV_MAX, "ion");
> +	if (ret) {
> +		pr_err("ion: unable to allocate device\n");
> +#ifdef CONFIG_ION_LEGACY_DEVICE_API
> +		misc_deregister(&idev->dev);
> +#endif
> +		kfree(idev);
> +		return ret;
> +	}
>  
>  	idev->debug_root = debugfs_create_dir("ion", NULL);
>  	if (!idev->debug_root) {

I'm not 100% sure about the device hierarchy here. We're
ending up with devices at the root of /sys/devices

/sys/devices # ls
breakpoint ion0 ion1 ion2 platform software system virtual 

and the Android init system doesn't pick this up. I'll
admit to being out of my area here but I don't think
this looks quite right.

Thanks,
Laura