Re: [PATCH v2 1/2] net: Add MHI Endpoint network driver

[Jeffrey Hugo]

On 6/7/2023 10:27 AM, Jeffrey Hugo wrote:
> On 6/7/2023 9:24 AM, Manivannan Sadhasivam wrote:
> > Add a network driver for the Modem Host Interface (MHI) endpoint devices
> > that provides network interfaces to the PCIe based Qualcomm endpoint
> > devices supporting MHI bus. This driver allows the MHI endpoint 
> > devices to
> > establish IP communication with the host machines (x86, ARM64) over MHI
> > bus.
> >
> > The driver currently supports only IP_SW0 MHI channel that can be used
> > to route IP traffic from the endpoint CPU to host machine.
> >
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> > ---
> >   drivers/net/Kconfig      |   9 ++
> >   drivers/net/Makefile     |   1 +
> >   drivers/net/mhi_ep_net.c | 331 +++++++++++++++++++++++++++++++++++++++
> >   3 files changed, 341 insertions(+)
> >   create mode 100644 drivers/net/mhi_ep_net.c
> >
> > diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> > index 368c6f5b327e..36b628e2e49f 100644
> > --- a/drivers/net/Kconfig
> > +++ b/drivers/net/Kconfig
> > @@ -452,6 +452,15 @@ config MHI_NET
> >         QCOM based WWAN modems for IP or QMAP/rmnet protocol (like 
> > SDX55).
> >         Say Y or M.
> > +config MHI_EP_NET
> > +    tristate "MHI Endpoint network driver"
> > +    depends on MHI_BUS_EP
> > +    help
> > +      This is the network driver for MHI bus implementation in endpoint
> > +      devices. It is used provide the network interface for QCOM 
> > endpoint
> > +      devices such as SDX55 modems.
> > +      Say Y or M.
>
> What will the module be called if "m" is selected?
>
> > +
> >   endif # NET_CORE
> >   config SUNGEM_PHY
> > diff --git a/drivers/net/Makefile b/drivers/net/Makefile
> > index e26f98f897c5..b8e706a4150e 100644
> > --- a/drivers/net/Makefile
> > +++ b/drivers/net/Makefile
> > @@ -40,6 +40,7 @@ obj-$(CONFIG_NLMON) += nlmon.o
> >   obj-$(CONFIG_NET_VRF) += vrf.o
> >   obj-$(CONFIG_VSOCKMON) += vsockmon.o
> >   obj-$(CONFIG_MHI_NET) += mhi_net.o
> > +obj-$(CONFIG_MHI_EP_NET) += mhi_ep_net.o
> >   #
> >   # Networking Drivers
> > diff --git a/drivers/net/mhi_ep_net.c b/drivers/net/mhi_ep_net.c
> > new file mode 100644
> > index 000000000000..0d7939caefc7
> > --- /dev/null
> > +++ b/drivers/net/mhi_ep_net.c
> > @@ -0,0 +1,331 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * MHI Endpoint Network driver
> > + *
> > + * Based on drivers/net/mhi_net.c
> > + *
> > + * Copyright (c) 2023, Linaro Ltd.
> > + * Author: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> > + */
> > +
> > +#include <linux/if_arp.h>
> > +#include <linux/mhi_ep.h>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/module.h>
> > +#include <linux/netdevice.h>
> > +#include <linux/skbuff.h>
> > +#include <linux/u64_stats_sync.h>
> > +
> > +#define MHI_NET_MIN_MTU        ETH_MIN_MTU
> > +#define MHI_NET_MAX_MTU        0xffff

ETH_MAX_MTU ?

Personal preference thing.  If you think 0xffff is really the superior 
option, so be it.  Personally, it takes me a second to figure out that 
is 64k - 1 and then relate it to the MHI packet size limit.  Also seems 
really odd with this line of code right next to, and related to, 
ETH_MIN_MTU.  Feels like a non-magic number here will make things more 
maintainable.

Alternatively move MHI_MAX_MTU out of host/internal.h into something 
that is convenient for this driver to include and use?  It is a 
fundamental constant for the MHI protocol, we just haven't yet had a 
need for it to be used outside of the MHI bus implementation code.

> > +
> > +struct mhi_ep_net_stats {
> > +    u64_stats_t rx_packets;
> > +    u64_stats_t rx_bytes;
> > +    u64_stats_t rx_errors;
> > +    u64_stats_t tx_packets;
> > +    u64_stats_t tx_bytes;
> > +    u64_stats_t tx_errors;
> > +    u64_stats_t tx_dropped;
> > +    struct u64_stats_sync tx_syncp;
> > +    struct u64_stats_sync rx_syncp;
> > +};
> > +
> > +struct mhi_ep_net_dev {
> > +    struct mhi_ep_device *mdev;
> > +    struct net_device *ndev;
> > +    struct mhi_ep_net_stats stats;
> > +    struct workqueue_struct *xmit_wq;
> > +    struct work_struct xmit_work;
> > +    struct sk_buff_head tx_buffers;
> > +    spinlock_t tx_lock; /* Lock for protecting tx_buffers */
> > +    u32 mru;
> > +};
> > +
> > +static void mhi_ep_net_dev_process_queue_packets(struct work_struct 
> > *work)
> > +{
> > +    struct mhi_ep_net_dev *mhi_ep_netdev = container_of(work,
> > +            struct mhi_ep_net_dev, xmit_work);
>
> Looks like this can fit all on one line to me.