On Friday 06 January 2017 08:25 PM, Thomas Monjalon wrote:
2017-01-06 16:01, Shreyansh Jain:
On Wednesday 04 January 2017 03:22 AM, Thomas Monjalon wrote:
2016-12-26 18:53, Shreyansh Jain:
+/**
+ * A structure describing a generic bus.
+ */
+struct rte_bus {
+ TAILQ_ENTRY(rte_bus) next; /**< Next bus object in linked list */
+ struct rte_driver_list driver_list;
+ /**< List of all drivers on bus */
+ struct rte_device_list device_list;
+ /**< List of all devices on bus */
+ const char *name; /**< Name of the bus */
+};
I am not convinced we should link a generic bus to drivers and devices.
What do you think of having rte_pci_bus being a rte_bus and linking
with rte_pci_device and rte_pci_driver lists?
This is different from what I had in mind.
You are saying:
Class: rte_bus
`-> No object instantiated for this class
Class: rte_pci_bus inheriting rte_bus
`-> object instantiated for this class.
Here, rte_bus is being treated as an abstract class which is only
inherited and rte_pci_bus is the base class which is instantiated.
And I was thinking:
Class: rte_bus
`-> Object: pci_bus (defined in */eal/eal_pci.c)
Here, rte_bus is that base class which is instantiated.
I agree that what you are suggesting is inline with current model:
rte_device -> abstract class (no one instantiates it)
`-> rte_pci_device -> Base class which inherits rte_device and
is instantiated.
Yes
When I choose not to create rte_pci_bus, it was because I didn't want
another indirection in form of rte_bus->rte_pci_bus->object.
There were no 'non-generic' bus functions which were only applicable for
rte_pci_bus. Eventually, rte_pci_bus ended up being a direct inheritance
of rte_bus.
I'm thinking to something like that:
struct rte_bus {
TAILQ_ENTRY(rte_bus) next;
const char *name;
rte_bus_scan_t scan;
rte_bus_match_t match;
};
struct rte_pci_bus {
struct rte_bus bus;
struct rte_pci_driver_list pci_drivers;
struct rte_pci_device_list pci_devices;
};
if we go by rte_bus->rte_pci_bus->(instance of rte_pci_bus), above is
fine. Though, I am in favor of rte_bus->(instance of rte_bus for PCI)
because I don't see any 'non-generic' information in rte_pci_bus which
can't be put in rte_bus.
The lists of drivers and devices are specific to the bus.
Your proposal was to list them as generic rte_driver/rte_device and
cast them. I'm just saying we can directly declare them with the right type,
e.g. rte_pci_driver/rte_pci_device.
Ok. I get your point. Already changing the code to reflect this.
In the same logic, the functions probe/remove are specifics for the bus and
should be declared in rte_pci_driver instead of the generic rte_driver.
Yes, I agree with this after above argument.
+/** Helper for Bus registration. The constructor has higher priority than
+ * PMD constructors
+ */
+#define RTE_REGISTER_BUS(nm, bus) \
+static void __attribute__((constructor(101), used)) businitfn_ ##nm(void) \
+{\
+ (bus).name = RTE_STR(nm);\
+ rte_eal_bus_register(&bus); \
+}
By removing the lists from rte_bus as suggested above, do you still need
a priority for this constructor?
I think yes.
Even if we have rte_pci_bus as a class, object of rte_bus should be part
of Bus list *before* registration of a driver (because, driver
registration searches for bus by name).
(This is assuming that no global PCI/VDEV/XXX bus object is created
which is directly used within all PCI specific bus operations).
There was another suggestion on list which was to check for existence of
bus _within_ each driver registration and create/instantiate an object
in case no bus is registered. I didn't like the approach so I didn't use
it. From David [1], and me [2]
[1] http://dpdk.org/ml/archives/dev/2016-December/051689.html
[2] http://dpdk.org/ml/archives/dev/2016-December/051698.html
OK, we can keep your approach of prioritize bus registrations.
If we see an issue later, we could switch to a bus registration done
when a first driver is registered on the bus.
Thanks for confirmation.
struct rte_device {
TAILQ_ENTRY(rte_device) next; /**< Next device */
+ struct rte_bus *bus; /**< Device connected to this bus */
const struct rte_driver *driver;/**< Associated driver */
int numa_node; /**< NUMA node connection */
struct rte_devargs *devargs; /**< Device user arguments */
@@ -148,6 +149,7 @@ void rte_eal_device_remove(struct rte_device *dev);
*/
struct rte_driver {
TAILQ_ENTRY(rte_driver) next; /**< Next in list. */
+ struct rte_bus *bus; /**< Bus serviced by this driver */
const char *name; /**< Driver name. */
const char *alias; /**< Driver alias. */
};
Do we need to know the bus associated to a driver in rte_driver?
Bus and driver are already associated in rte_device.
Two reasons:
1/ A driver should be associated with a bus so that if required, all bus
can be directly extracted - even when probing has not been done.
I do not understand this need.
For example, Looping over all drivers for plugging them out. We need to
know which bus a driver is on so that we can unplug the devices
associated with the driver on that bus.
2/ device->driver would only be updated after probe. device->driver->bus
would not be valid in such cases, if required.
We can update device->driver on match.
Yes, we can.
Please let's do not over-engineer if not needed.
In this case, I think we can skip rte_driver->bus.
Hm, Ok. This was more of prospective step. We can avoid it without much
impact. I will change the code.
Overall, I don't have objections for rte_bus->rte_pci_bus=>object as
compared to rte_bus=>PCI-object. But, I would still like to get a final
confirmation of a more preferred way.
Meanwhile, I will make changes to accommodate this change to save time
in case rte_pci_bus class is final/preferred method.
It looks more natural to me to avoid class casting and use specialized classes
when possible. So yes I prefer instantiating rte_pci_bus.
However, I could be wrong, and will consider any argument.
Ok. I will go with your argument - mostly because I am OK either way and
we can always come back if framework changes are stable.
Thanks
