Re: [PATCHv3 2/6] mailbox: Introduce a new common API

Greg KH
2014-02-15T19:13:54Z

On Sat, Feb 15, 2014 at 11:55:27PM +0530, Jassi Brar wrote:
> +/*
> + * Call for IPC controller drivers to register a controller, adding
> + * its channels/mailboxes to the global pool.
> + */
> +int ipc_links_register(struct ipc_controller *ipc)
> +{
> + int i, num_links, txdone;
> + struct ipc_chan *chan;
> + struct ipc_con *con;
> +
> + /* Sanity check */
> + if (!ipc || !ipc->ops)
> + return -EINVAL;
> +
> + for (i = 0; ipc->links[i]; i++)
> + ;
> + if (!i)
> + return -EINVAL;

So you have to have links? You should document this in the function
definition. Actually, why no kerneldoc for the public functions?

> + num_links = i;
> +
> + mutex_lock(&con_mutex);
> + /* Check if already populated */
> + list_for_each_entry(con, &ipc_cons, node)
> + if (!strcmp(ipc->controller_name, con->name)) {
> + mutex_unlock(&con_mutex);
> + return -EINVAL;
> + }
> + mutex_unlock(&con_mutex);

Why drop the lock here? Shouldn't you grab it for the whole function,
as this could race if two callers want to register the same name.

> + con = kzalloc(sizeof(*con) + sizeof(*chan) * num_links, GFP_KERNEL);

Are you ok with structures on unaligned boundries? That might really
slow down some processors if your pointers are unaligned...

> + if (!con)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&con->channels);
> + snprintf(con->name, 16, "%s", ipc->controller_name);

Magic name size :(

> +
> + if (ipc->txdone_irq)
> + txdone = TXDONE_BY_IRQ;
> + else if (ipc->txdone_poll)
> + txdone = TXDONE_BY_POLL;
> + else /* It has to be ACK then */
> + txdone = TXDONE_BY_ACK;
> +
> + if (txdone == TXDONE_BY_POLL) {
> + con->period = ipc->txpoll_period;
> + con->poll.function = &poll_txdone;
> + con->poll.data = (unsigned long)con;
> + init_timer(&con->poll);
> + }
> +
> + chan = (void *)con + sizeof(*con);
> + for (i = 0; i < num_links; i++) {
> + chan[i].con = con;
> + chan[i].assigned = false;
> + chan[i].link_ops = ipc->ops;
> + chan[i].link = ipc->links[i];
> + chan[i].txdone_method = txdone;
> + chan[i].link->api_priv = &chan[i];
> + spin_lock_init(&chan[i].lock);
> + BLOCKING_INIT_NOTIFIER_HEAD(&chan[i].avail);
> + list_add_tail(&chan[i].node, &con->channels);
> + snprintf(chan[i].name, 16, "%s", ipc->links[i]->link_name);

Magic name size :(

> + }
> +
> + mutex_lock(&con_mutex);
> + list_add_tail(&con->node, &ipc_cons);
> + mutex_unlock(&con_mutex);

You could have raced with above, please just grab the lock for the
whole call to be safe.

> +
> + return 0;
> +}
> +EXPORT_SYMBOL(ipc_links_register);
> +
> +void ipc_links_unregister(struct ipc_controller *ipc)
> +{
> + struct ipc_con *t, *con = NULL;
> + struct ipc_chan *chan;
> +
> + mutex_lock(&con_mutex);
> +
> + list_for_each_entry(t, &ipc_cons, node)
> + if (!strcmp(ipc->controller_name, t->name)) {
> + con = t;
> + break;
> + }
> +
> + if (con)
> + list_del(&con->node);
> +
> + mutex_unlock(&con_mutex);
> +
> + if (!con)
> + return;
> +
> + list_for_each_entry(chan, &con->channels, node)
> + ipc_free_channel((void *)chan);

Why does this function take a void *? Shouldn't it take a "real"
structure pointer?

> +
> + del_timer_sync(&con->poll);
> +
> + kfree(con);
> +}
> +EXPORT_SYMBOL(ipc_links_unregister);

> +struct ipc_client {
> + char *chan_name;
> + void *cl_id;

Why a void *? Can't you have a "real" type here?

> + void (*rxcb)(void *cl_id, void *mssg);
> + void (*txcb)(void *cl_id, void *mssg, enum xfer_result r);
> + bool tx_block;
> + unsigned long tx_tout;
> + bool knows_txdone;
> + void *link_data;
> +};
> +
> +/**
> + * The Client specifies its requirements and capabilities while asking for
> + * a channel/mailbox by name. It can't be called from atomic context.
> + * The channel is exclusively allocated and can't be used by another
> + * client before the owner calls ipc_free_channel.
> + */
> +void *ipc_request_channel(struct ipc_client *cl);

Can't you return a real type, and use it everywhere? That's much
"safer" and nicer. This isn't other operating systems that have void *
everywhere and handles, we have real types in Linux :)

thanks,

greg k-h