Re: [PATCH v9 06/19] vfio/platform: return info for bound device

[Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On 11/20/2014 03:10 PM, Antonios Motakis wrote:
> On Wed, Nov 12, 2014 at 5:36 PM, Alex Williamson
> <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>> On Wed, 2014-11-12 at 11:32 +0100, Eric Auger wrote:
>>> On 10/27/2014 07:07 PM, Antonios Motakis wrote:
>>>> A VFIO userspace driver will start by opening the VFIO device
>>>> that corresponds to an IOMMU group, and will use the ioctl interface
>>>> to get the basic device info, such as number of memory regions and
>>>> interrupts, and their properties. This patch enables the
>>>> VFIO_DEVICE_GET_INFO ioctl call.
>>>>
>>>> Signed-off-by: Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>
>>>> ---
>>>>  drivers/vfio/platform/vfio_platform_common.c | 23 ++++++++++++++++++++---
>>>>  1 file changed, 20 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
>>>> index e0fdbc8..cb20526 100644
>>>> --- a/drivers/vfio/platform/vfio_platform_common.c
>>>> +++ b/drivers/vfio/platform/vfio_platform_common.c
>>>> @@ -43,10 +43,27 @@ static int vfio_platform_open(void *device_data)
>>>>  static long vfio_platform_ioctl(void *device_data,
>>>>                        unsigned int cmd, unsigned long arg)
>>>>  {
>>>> -   if (cmd == VFIO_DEVICE_GET_INFO)
>>>> -           return -EINVAL;
>>>> +   struct vfio_platform_device *vdev = device_data;
>>>> +   unsigned long minsz;
>>>> +
>>>> +   if (cmd == VFIO_DEVICE_GET_INFO) {
>>>> +           struct vfio_device_info info;
>>>> +
>>>> +           minsz = offsetofend(struct vfio_device_info, num_irqs);
>>>> +
>>>> +           if (copy_from_user(&info, (void __user *)arg, minsz))
>>>> +                   return -EFAULT;
>>>> +
>>>> +           if (info.argsz < minsz)
>>>> +                   return -EINVAL;
>>>> +
>>>> +           info.flags = vdev->flags;
>>>> +           info.num_regions = 0;
>>>> +           info.num_irqs = 0;
>>> Seems a bit weird to me to enable the modality but returning zeroed
>>> values. Shouldn't we put that patch after VFIO_DEVICE_GET_REGION_INFO
>>> and VFIO_DEVICE_GET_IRQ_INFO ones?
>>
>> I actually like how Antonios has started from a base framework, exposing
>> a device but none of the resources and then incrementally adds each
>> component.  It's also a good showcase of the VFIO ABI that we can do
>> things like this.  Thanks,
> 
> I also agree with Alex with this. But of course I'm not married with
> any particular splitting style, in case we decide to change this.

Hi Antonios,
please keep as is. I also learn each day about splitting style ;-)
Best Regards
Eric
> 
>>
>> Alex
>>