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    SubjectRe: [PATCH v2 6/6] tilegx network driver: initial support
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    On Friday 06 April 2012, Chris Metcalf wrote:
    > This change adds support for the tilegx network driver based on the
    > GXIO IORPC support in the tilegx software stack, using the on-chip
    > mPIPE packet processing engine.
    >
    > Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

    All my previous comments have been addressed. A few more details
    that I noticed only now:


    > +/* A mutex for "tile_net_devs_for_channel". */
    > +static struct mutex tile_net_devs_for_channel_mutex;

    static DEFINE_MUTEX()

    > +/* The per-cpu info. */
    > +static DEFINE_PER_CPU(struct tile_net_info, per_cpu_info);
    > +
    > +/* Access to "per_cpu_info". */
    > +static struct tile_net_info *infos[NR_CPUS];

    The arrays should not be needed. Using per_cpu() on the variable
    in front of it does the same.

    > +static int __init network_cpus_setup(char *str)
    > +{
    > + int rc = cpulist_parse_crop(str, &network_cpus_map);
    > + if (rc != 0) {
    > + pr_warning("network_cpus=%s: malformed cpu list\n",
    > + str);
    > + } else {
    > +
    > + /* Remove dedicated cpus. */
    > + cpumask_and(&network_cpus_map, &network_cpus_map,
    > + cpu_possible_mask);
    > +
    > +
    > + if (cpumask_empty(&network_cpus_map)) {
    > + pr_warning("Ignoring network_cpus='%s'.\n", str);
    > + } else {
    > + char buf[1024];
    > + cpulist_scnprintf(buf, sizeof(buf), &network_cpus_map);
    > + pr_info("Linux network CPUs: %s\n", buf);
    > + network_cpus_used = true;
    > + }
    > + }
    > +
    > + return 0;
    > +}
    > +__setup("network_cpus=", network_cpus_setup);

    In device drivers, use module_param() instead of __setup() so that you can
    set the arguments on the kernel command line and using modprobe with the
    same syntax.

    > +/* This function takes "skb", consisting of a header template and a
    > + * (presumably) huge payload, and egresses it as one or more segments
    > + * (aka packets), each consisting of a (possibly modified) copy of the
    > + * header plus a piece of the payload, via "tcp segmentation offload".
    > + *
    > + * Usually, "data" will contain the header template, of size "sh_len",
    > + * and "sh->frags" will contain "skb->data_len" bytes of payload, and
    > + * there will be "sh->gso_segs" segments.
    > + *
    > + * Sometimes, if "sendfile()" requires copying, we will be called with
    > + * "data" containing the header and payload, with "frags" being empty.
    > + *
    > + * Sometimes, for example when using NFS over TCP, a single segment can
    > + * span 3 fragments. This requires special care below.
    > + *
    > + * See "emulate_large_send_offload()" for some reference code, which
    > + * does not handle checksumming.
    > + */
    > +static int tile_net_tx_tso(struct sk_buff *skb, struct net_device *dev)
    > +{

    This function seems too long to be readable. I would suggest splitting
    out some of the loop bodies in it into separate functions.

    Arnd



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