Re: [RFC net-next 8/8] net/mlx5: Add subdev driver to bind to subdev devices

[Saeed Mahameed]

On Thu, 2019-02-28 at 23:37 -0600, Parav Pandit wrote:
> Add a subdev driver to probe the subdev devices and create fake
> netdevice for it.
> 
> Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/Makefile   |  2 +-
>  drivers/net/ethernet/mellanox/mlx5/core/main.c     |  8 +-
>  .../net/ethernet/mellanox/mlx5/core/mlx5_core.h    |  3 +
>  .../ethernet/mellanox/mlx5/core/subdev_driver.c    | 93
> ++++++++++++++++++++++
>  4 files changed, 104 insertions(+), 2 deletions(-)
>  create mode 100644
> drivers/net/ethernet/mellanox/mlx5/core/subdev_driver.c
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/Makefile
> b/drivers/net/ethernet/mellanox/mlx5/core/Makefile
> index f218789..c8aeaf1 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/Makefile
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/Makefile
> @@ -16,7 +16,7 @@ mlx5_core-y :=	main.o cmd.o debugfs.o fw.o
> eq.o uar.o pagealloc.o \
>  		transobj.o vport.o sriov.o fs_cmd.o fs_core.o \
>  		fs_counters.o rl.o lag.o dev.o events.o wq.o lib/gid.o
> \
>  		lib/devcom.o diag/fs_tracepoint.o diag/fw_tracer.o
> -mlx5_core-$(CONFIG_SUBDEV) += subdev.o
> +mlx5_core-$(CONFIG_SUBDEV) += subdev.o subdev_driver.o
>  
>  #
>  # Netdev basic
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c
> b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> index 5f8cf0d..7dfa8c4 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> @@ -1548,7 +1548,11 @@ static int __init init(void)
>  	mlx5e_init();
>  #endif
>  
> -	return 0;
> +	err = subdev_register_driver(&mlx5_subdev_driver);
> +	if (err)
> +		pci_unregister_driver(&mlx5_core_driver);
> +
> +	return err;
>  
>  err_debug:
>  	mlx5_unregister_debugfs();
> @@ -1557,6 +1561,8 @@ static int __init init(void)
>  
>  static void __exit cleanup(void)
>  {
> +	subdev_unregister_driver(&mlx5_subdev_driver);
> +
>  #ifdef CONFIG_MLX5_CORE_EN
>  	mlx5e_cleanup();
>  #endif
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
> b/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
> index 2a54148..1b733c7 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.h
> @@ -41,12 +41,15 @@
>  #include <linux/ptp_clock_kernel.h>
>  #include <linux/mlx5/cq.h>
>  #include <linux/mlx5/fs.h>
> +#include <linux/subdev_bus.h>
>  
>  #define DRIVER_NAME "mlx5_core"
>  #define DRIVER_VERSION "5.0-0"
>  
>  extern uint mlx5_core_debug_mask;
>  
> +extern struct subdev_driver mlx5_subdev_driver;
> +
>  #define mlx5_core_dbg(__dev, format, ...)				
> \
>  	dev_dbg(&(__dev)->pdev->dev, "%s:%d:(pid %d): " format,		
> \
>  		 __func__, __LINE__, current->pid,			
> \
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/subdev_driver.c
> b/drivers/net/ethernet/mellanox/mlx5/core/subdev_driver.c
> new file mode 100644
> index 0000000..880aa4f
> --- /dev/null
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/subdev_driver.c
> @@ -0,0 +1,93 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2018-19 Mellanox Technologies
> +
> +#include <linux/module.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/subdev_bus.h>
> +#include <linux/subdev_ids.h>
> +#include <linux/etherdevice.h>
> +
> +struct mlx5_subdev_ndev {
> +	struct net_device ndev;
> +};
> +
> +static void mlx5_dma_test(struct device *dev)
> +{
> +	dma_addr_t pa;
> +	void *va;
> +
> +	va = dma_alloc_coherent(dev, 4096, &pa, GFP_KERNEL);
> +	if (va)
> +		dma_free_coherent(dev, 4096, va, pa);
> +}
> +
> +static struct net_device *ndev;
> +
> +static int mlx5e_subdev_open(struct net_device *netdev)
> +{
> +	return 0;
> +}
> +
> +static int mlx5e_subdev_close(struct net_device *netdev)
> +{
> +	return 0;
> +}
> +
> +static netdev_tx_t
> +mlx5e_subdev_xmit(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	return NETDEV_TX_BUSY;
> +}
> +
> +const struct net_device_ops mlx5e_subdev_netdev_ops = {
> +	.ndo_open                = mlx5e_subdev_open,
> +	.ndo_stop                = mlx5e_subdev_close,
> +	.ndo_start_xmit          = mlx5e_subdev_xmit,
> +};
> +
> +static int mlx5_subdev_probe(struct device *dev)
> +{
> +	int err;
> +
> +	mlx5_dma_test(dev);

Hi Parav, can you please shed some light on how do you plan to
communicate with the parent device ? (pci_dev and it's running driver
instance), We will need to share some resources, such as IRQs/BARs/etc
.., and maybe some HW objects which are going to be managed by the
parent pci device driver.

Just allocating a dma buffer doesn't mean anything, the dma buffer is
just bound to the generic device.

> +	/* Only one device supported in rfc */
> +	if (ndev)
> +		return 0;
> +
> +	ndev = alloc_etherdev_mqs(sizeof(struct mlx5_subdev_ndev), 1,
> 1);
> +	if (!ndev)
> +		return -ENOMEM;
> +
> +	SET_NETDEV_DEV(ndev, dev);
> +	ndev->netdev_ops = &mlx5e_subdev_netdev_ops;
> +	err = register_netdev(ndev);
> +	if (err) {
> +		free_netdev(ndev);
> +		ndev = NULL;
> +	}
> +	return err;
> +}
> +
> +static int mlx5_subdev_remove(struct device *dev)
> +{
> +	if (ndev) {
> +		unregister_netdev(ndev);
> +		free_netdev(ndev);
> +		ndev = NULL;
> +	}
> +	return 0;
> +}
> +
> +static const struct subdev_id mlx5_subdev_id_table[] = {
> +	{ .vendor_id = SUBDEV_VENDOR_ID_MELLANOX,
> +	  .device_id = SUBDEV_DEVICE_ID_MELLANOX_SF },
> +	{ 0, }
> +};
> +MODULE_DEVICE_TABLE(subdev, mlx5_subdev_id_table);
> +
> +struct subdev_driver mlx5_subdev_driver = {
> +	.id_table = mlx5_subdev_id_table,
> +	.driver.name = "mlx5_subdev_driver",
> +	.driver.probe = mlx5_subdev_probe,
> +	.driver.remove = mlx5_subdev_remove,
> +};