[dpdk-dev] [PATCH v2 01/11] bus: add bus iterator to find a particular bus

[Gaëtan Rivet]

On Wed, Jun 07, 2017 at 12:36:53PM +0530, Shreyansh Jain wrote:
> Hello Gaetan,
> 
> On Wednesday 31 May 2017 06:47 PM, Gaetan Rivet wrote:
> >From: Jan Blunck <jblunck at infradead.org>
> >
> >Signed-off-by: Jan Blunck <jblunck at infradead.org>
> >Signed-off-by: Gaetan Rivet <gaetan.rivet at 6wind.com>
> >---
> >  lib/librte_eal/bsdapp/eal/rte_eal_version.map   |  1 +
> >  lib/librte_eal/common/eal_common_bus.c          | 13 ++++++++++
> >  lib/librte_eal/common/include/rte_bus.h         | 32 +++++++++++++++++++++++++
> >  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  1 +
> >  4 files changed, 47 insertions(+)
> >
> >diff --git a/lib/librte_eal/bsdapp/eal/rte_eal_version.map b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >index 2e48a73..ed09ab2 100644
> >--- a/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >+++ b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> >@@ -162,6 +162,7 @@ DPDK_17.02 {
> >  DPDK_17.05 {
> >  	global:
> >+	rte_bus_find;
> >  	rte_cpu_is_supported;
> >  	rte_log_dump;
> >  	rte_log_register;
> >diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c
> >index 8f9baf8..68f70d0 100644
> >--- a/lib/librte_eal/common/eal_common_bus.c
> >+++ b/lib/librte_eal/common/eal_common_bus.c
> >@@ -145,3 +145,16 @@ rte_bus_dump(FILE *f)
> >  		}
> >  	}
> >  }
> >+
> >+struct rte_bus *
> >+rte_bus_find(rte_bus_match_t match, const void *data)
> >+{
> >+	struct rte_bus *bus = NULL;
> >+
> >+	TAILQ_FOREACH(bus, &rte_bus_list, next) {
> >+		if (match(bus, data))
> >+			break;
> >+	}
> >+
> >+	return bus;
> >+}
> >diff --git a/lib/librte_eal/common/include/rte_bus.h b/lib/librte_eal/common/include/rte_bus.h
> >index 7c36969..006feca 100644
> >--- a/lib/librte_eal/common/include/rte_bus.h
> >+++ b/lib/librte_eal/common/include/rte_bus.h
> >@@ -141,6 +141,38 @@ int rte_bus_probe(void);
> >  void rte_bus_dump(FILE *f);
> >  /**
> >+ * Bus match function.
> >+ *
> >+ * @param bus
> >+ *	bus under test.
> >+ *
> >+ * @param data
> >+ *	data matched
> >+ *
> >+ * @return
> >+ *	0 if the bus does not match.
> >+ *	!0 if the bus matches.
> 
> One of the common match function implementation could be simply to match
> a string. strcmp itself returns '0' for a successful match.
> On the same lines, should this function return value be reversed?
> -
> 0 if match
> !0 if not a match
> -
> That way, people would not have to change either the way strcmp works,
> for example, or the way various APIs expect '0' as success.
> 
> same for rte_device_match_t as well. (in next patch)
> 

It was actually a point I hesitated a little before submitting this
version.

The logic behind strcmp is that you can express three states: greater
than, equal, lower than, thus having total order within the string set.

Here, buses are not ordered (logically). Having a bus lower or greater
than some arbitrary data does not mean much.

Anyway, this was my reasoning for following Jan's proposal on this, but
I'm not against changing this API. Maybe having to possibility to
express total order could be useful eventually. I don't have a strong
opinion on this so unless someone shouts about it, I will follow your
remark.

> >+ */
> >+typedef int (*rte_bus_match_t)(const struct rte_bus *bus, const void *data);
> >+
> >+/**
> >+ * Bus iterator to find a particular bus.
> >+ *
> >+ * If the callback returns non-zero this function will stop iterating over
> >+ * any more buses.
> >+ *
> >+ * @param match
> >+ *	 Callback function to check bus
> >+ *
> >+ * @param data
> >+ *	 Data to pass to match callback
> >+ *
> >+ * @return
> >+ *	 A pointer to a rte_bus structure or NULL in case no bus matches
> >+ */
> >+struct rte_bus *rte_bus_find(rte_bus_match_t match, const void *data);
> >+
> >+/**
> >   * Helper for Bus registration.
> >   * The constructor has higher priority than PMD constructors.
> >   */
> >diff --git a/lib/librte_eal/linuxapp/eal/rte_eal_version.map b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >index 670bab3..6efa517 100644
> >--- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >+++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> >@@ -166,6 +166,7 @@ DPDK_17.02 {
> >  DPDK_17.05 {
> >  	global:
> >+	rte_bus_find;
> >  	rte_cpu_is_supported;
> >  	rte_intr_free_epoll_fd;
> >  	rte_log_dump;
> >

-- 
Gaëtan Rivet
6WIND