Re: [RFC PATCH 01/10] vdpa: add get_config_size callback in vdpa_config_ops

On Thu, Mar 04, 2021 at 04:34:52PM +0800, Jason Wang wrote:

On 2021/3/2 10:15 下午, Stefano Garzarella wrote:

quoted

On Tue, Mar 02, 2021 at 12:14:13PM +0800, Jason Wang wrote:

quoted

On 2021/2/16 5:44 下午, Stefano Garzarella wrote:

quoted

This new callback is used to get the size of the configuration space
of vDPA devices.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
include/linux/vdpa.h              | 4 ++++
drivers/vdpa/ifcvf/ifcvf_main.c   | 6 ++++++
drivers/vdpa/mlx5/net/mlx5_vnet.c | 6 ++++++
drivers/vdpa/vdpa_sim/vdpa_sim.c  | 9 +++++++++
4 files changed, 25 insertions(+)

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 4ab5494503a8..fddf42b17573 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h

@@ -150,6 +150,9 @@ struct vdpa_iova_range {
 * @set_status:            Set the device status
 *                @vdev: vdpa device
 *                @status: virtio device status
+ * @get_config_size:        Get the size of the configuration space
+ *                @vdev: vdpa device
+ *                Returns size_t: configuration size

Rethink about this, how much we could gain by introducing a 
dedicated ops here? E.g would it be simpler if we simply introduce 
a max_config_size to vdpa device?

Mainly because in this way we don't have to add new parameters to 
the vdpa_alloc_device() function.

We do the same for example for 'get_device_id', 'get_vendor_id', 
'get_vq_num_max'. All of these are usually static, but we have ops.
I think because it's easier to extend.

I don't know if it's worth adding a new structure for these static 
values at this point, like 'struct vdpa_config_params'.

Yes, that's the point. I think for any static values, it should be set 
during device allocation.

Yeah, I see.

I'm fine with both.

@Michael any thoughts?

Thanks,
Stefano

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