Hi Andrew,
On Mon, 2023-07-03 at 16:43 +0200, Andrew Lunn wrote:
> > +#define MCTP_I3C_MAXBUF 65536
> > +/* 48 bit Provisioned Id */
> > +#define PID_SIZE 6
> > +
> > +/* 64 byte payload, 4 byte MCTP header */
> > +static const int MCTP_I3C_MINMTU = 64 + 4;
> > +/* One byte less to allow for the PEC */
> > +static const int MCTP_I3C_MAXMTU = MCTP_I3C_MAXBUF - 1;
> > +/* 4 byte MCTP header, no data, 1 byte PEC */
> > +static const int MCTP_I3C_MINLEN = 4 + 1;
>
> Why static const and not #define? It would also be normal for
> variables to be lower case, to make it clear they are in fact
> variables, not #defines.
My personal preference is for static const since it's less error prone,
though had to use #define for the ones used in array sizing. Happy to change
to #define if that's the style though.
> > +struct mctp_i3c_bus {
> > + struct net_device *ndev;
> > +
> > + struct task_struct *tx_thread;
> > + wait_queue_head_t tx_wq;
> > + /* tx_lock protects tx_skb and devs */
> > + spinlock_t tx_lock;
> > + /* Next skb to transmit */
> > + struct sk_buff *tx_skb;
> > + /* Scratch buffer for xmit */
> > + u8 tx_scratch[MCTP_I3C_MAXBUF];
> > +
> > + /* Element of busdevs */
> > + struct list_head list;
> > +
> > + /* Provisioned ID of our controller */
> > + u64 pid;
> > +
> > + struct i3c_bus *bus;
> > + /* Head of mctp_i3c_device.list. Protected by busdevs_lock */
> > + struct list_head devs;
> > +};
> > +
> > +struct mctp_i3c_device {
> > + struct i3c_device *i3c;
> > + struct mctp_i3c_bus *mbus;
> > + struct list_head list; /* Element of mctp_i3c_bus.devs */
> > +
> > + /* Held while tx_thread is using this device */
> > + struct mutex lock;
> > +
> > + /* Whether BCR indicates MDB is present in IBI */
> > + bool have_mdb;
> > + /* I3C dynamic address */
> > + u8 addr;
> > + /* Maximum read length */
> > + u16 mrl;
> > + /* Maximum write length */
> > + u16 mwl;
> > + /* Provisioned ID */
> > + u64 pid;
> > +};
>
> Since you have commented about most of the members of these
> structures, you could use kerneldoc.
These aren't intended to be exposed as an API anywhere, just commented
for future code readers (including me). Is kerneldoc still appropriate?
>
> > +/* We synthesise a mac header using the Provisioned ID.
> > + * Used to pass dest to mctp_i3c_start_xmit.
> > + */
> > +struct mctp_i3c_internal_hdr {
> > + u8 dest[PID_SIZE];
> > + u8 source[PID_SIZE];
> > +} __packed;
> > +
> > +/* Returns the 48 bit Provisioned Id from an i3c_device_info.pid */
> > +static void pid_to_addr(u64 pid, u8 addr[PID_SIZE])
> > +{
> > + pid = cpu_to_be64(pid);
> > + memcpy(addr, ((u8 *)&pid) + 2, PID_SIZE);
> > +}
> > +
> > +static u64 addr_to_pid(u8 addr[PID_SIZE])
> > +{
> > + u64 pid = 0;
> > +
> > + memcpy(((u8 *)&pid) + 2, addr, PID_SIZE);
> > + return be64_to_cpu(pid);
> > +}
>
> I don't know anything about MCTP. But Ethernet MAC addresses are also
> 48 bits. Could you make use of u64_to_ether_addr() and ether_addr_to_u64()?
The 48 bit identifier is an I3C Provisioned ID. It has a similar purpose to
an ethernet MAC address but for a different protocol. I think it might cause
confusion to code readers if it were passed to ethernet functions.
>
> > +static int mctp_i3c_setup(struct mctp_i3c_device *mi)
> > +{
> > + const struct i3c_ibi_setup ibi = {
> > + .max_payload_len = 1,
> > + .num_slots = MCTP_I3C_IBI_SLOTS,
> > + .handler = mctp_i3c_ibi_handler,
> > + };
> > + bool ibi_set = false, ibi_enabled = false;
> > + struct i3c_device_info info;
> > + int rc;
> > +
> > + i3c_device_get_info(mi->i3c, &info);
> > + mi->have_mdb = info.bcr & BIT(2);
> > + mi->addr = info.dyn_addr;
> > + mi->mwl = info.max_write_len;
> > + mi->mrl = info.max_read_len;
> > + mi->pid = info.pid;
> > +
> > + rc = i3c_device_request_ibi(mi->i3c, &ibi);
> > + if (rc == 0) {
> > + ibi_set = true;
> > + } else if (rc == -ENOTSUPP) {
>
> In networking, we try to avoid ENOTSUPP and use EOPNOTSUPP:
>
> https://lore.kernel.org/netdev/20200511165319.2251678-1-kuba@xxxxxxxxxx/
checkpatch noticed this one too, but the existing I3C functions return
ENOTSUPP so it needs to match against that.
> > +static int mctp_i3c_header_create(struct sk_buff *skb, struct net_device
> > *dev,
> > + unsigned short type, const void
> > *daddr,
> > + const void *saddr, unsigned int len)
> > +{
> > + struct mctp_i3c_internal_hdr *ihdr;
> > +
> > + skb_push(skb, sizeof(struct mctp_i3c_internal_hdr));
> > + skb_reset_mac_header(skb);
> > + ihdr = (void *)skb_mac_header(skb);
> > + memcpy(ihdr->dest, daddr, PID_SIZE);
> > + memcpy(ihdr->source, saddr, PID_SIZE);
>
> ether_addr_copy() ?
>
> > +/* Returns an ERR_PTR on failure */
> > +static struct mctp_i3c_bus *mctp_i3c_bus_add(struct i3c_bus *bus)
> > +__must_hold(&busdevs_lock)
> > +{
> > + struct mctp_i3c_bus *mbus = NULL;
> > + struct net_device *ndev = NULL;
> > + u8 addr[PID_SIZE];
> > + char namebuf[IFNAMSIZ];
> > + int rc;
> > +
> > + if (!mctp_i3c_is_mctp_controller(bus))
> > + return ERR_PTR(-ENOENT);
> > +
> > + snprintf(namebuf, sizeof(namebuf), "mctpi3c%d", bus->id);
> > + ndev = alloc_netdev(sizeof(*mbus), namebuf, NET_NAME_ENUM,
> > mctp_i3c_net_setup);
> > + if (!ndev) {
> > + pr_warn("No memory for %s\n", namebuf);
>
> pr_ functions are not liked too much. Is there a struct device you can
> use with dev_warn()?
I'll change the ones with a device available, that one in particular can be
removed anyway.
Thanks,
Matt
