[EARLY RFC][PATCH 3/4] ion: Add HEAP_INFO ioctl to be able to fetch heap type

[Laura Abbott]

On 2/15/19 12:24 PM, John Stultz wrote:
> The per-device heaps don't support HEAP_QUERY ioctl, since
> the name is provided in the devnode path and the heapid isn't
> useful with the new interface (one uses the fd of heapdevice).
> 
> But, one missing bit of functionality is a way to find the
> heap type. So provide a HEAP_INFO ioctl which exposes the
> heap type out so there is the potential for some sort of
> dynamic heap matching/discovery.
> 
> Most likely this IOCTL will be useful when extended to allow
> some sort of opaque constraint bitfield to be shared so userland
> can match heaps with devices in a fully dynamic way.
> 

We've been waiting on the constraint solving for a while and
it's never really happened :(

It certainly works but I'm concerned about adding this and
then finding (yet again) that it doesn't work. We're
getting the heap name now but do we lose anything if we
don't expose it as part of the ABI?

> Cc: Laura Abbott <labbott at redhat.com>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: Liam Mark <lmark at codeaurora.org>
> Cc: Brian Starkey <Brian.Starkey at arm.com>
> Cc: Andrew F. Davis <afd at ti.com>
> Cc: Alistair Strachan <astrachan at google.com>
> Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: John Stultz <john.stultz at linaro.org>
> ---
>   drivers/staging/android/ion/ion-ioctl.c | 12 ++++++++++++
>   drivers/staging/android/uapi/ion.h      | 22 ++++++++++++++++++++++
>   2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/staging/android/ion/ion-ioctl.c b/drivers/staging/android/ion/ion-ioctl.c
> index ea8d263..6db5969 100644
> --- a/drivers/staging/android/ion/ion-ioctl.c
> +++ b/drivers/staging/android/ion/ion-ioctl.c
> @@ -14,6 +14,7 @@ union ion_ioctl_arg {
>   	struct ion_allocation_data allocation;
>   	struct ion_heap_allocation_data heap_allocation;
>   	struct ion_heap_query query;
> +	struct ion_heap_info heap_info;
>   	u32 version;
>   };
>   
> @@ -149,6 +150,17 @@ long ion_heap_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>   
>   		break;
>   	}
> +	case ION_IOC_HEAP_INFO:
> +	{
> +		struct miscdevice *miscdev = filp->private_data;
> +		struct ion_heap *heap;
> +
> +		heap = container_of(miscdev, struct ion_heap, heap_dev);
> +
> +		data.heap_info.type = heap->type;
> +
> +		break;
> +	}
>   	case ION_IOC_VERSION:
>   		data.version = ION_VERSION;
>   		break;
> diff --git a/drivers/staging/android/uapi/ion.h b/drivers/staging/android/uapi/ion.h
> index 20db09f..1b3ca1e 100644
> --- a/drivers/staging/android/uapi/ion.h
> +++ b/drivers/staging/android/uapi/ion.h
> @@ -111,6 +111,19 @@ struct ion_heap_data {
>   };
>   
>   /**
> + * struct ion_heap_info - Info about the heap
> + *
> + */
> +struct ion_heap_info {
> +	__u32 type;
> +	__u32 reserved0;
> +	__u32 reserved1;
> +	__u32 reserved2;
> +	__u32 reserved3;
> +	__u32 reserved4;
> +};
> +
> +/**
>    * struct ion_heap_query - collection of data about all heaps
>    * @cnt - total number of heaps to be copied
>    * @heaps - buffer to copy heap data
> @@ -159,4 +172,13 @@ struct ion_heap_query {
>   #define ION_IOC_HEAP_ALLOC	_IOWR(ION_IOC_MAGIC, 10, \
>   				      struct ion_heap_allocation_data)
>   
> +/**
> + * DOC: ION_IOC_HEAP_INFO - allocate memory from heap
> + *
> + * Takes an ion_heap_query structure and populates information about
> + * available Ion heaps.
> + */
> +#define ION_IOC_HEAP_INFO	_IOWR(ION_IOC_MAGIC, 11, \
> +				      struct ion_heap_allocation_data)
> +
>   #endif /* _UAPI_LINUX_ION_H */
>