Re: [PATCH v5 05/12] eal: add probe and remove support for rte_driver

From: Shreyansh Jain <shreyansh.jain@nxp.com>
To: Thomas Monjalon <thomas.monjalon@6wind.com>
Cc: <david.marchand@6wind.com>, <dev@dpdk.org>
Subject: Re: [PATCH v5 05/12] eal: add probe and remove support for rte_driver
Date: Mon, 9 Jan 2017 11:58:27 +0530	[thread overview]
Message-ID: <25261ee3-120f-7821-0217-35bfec3bc0fb@nxp.com> (raw)
In-Reply-To: <2232398.sT6R6nRinv@xps13>

On Friday 06 January 2017 08:56 PM, Thomas Monjalon wrote:
> 2017-01-06 17:14, Shreyansh Jain:
>> On Wednesday 04 January 2017 03:35 AM, Thomas Monjalon wrote:
>>> 2016-12-26 18:53, Shreyansh Jain:
>>>> --- a/lib/librte_eal/common/include/rte_dev.h
>>>> +++ b/lib/librte_eal/common/include/rte_dev.h
>>>> @@ -152,6 +162,8 @@ struct rte_driver {
>>>>  	struct rte_bus *bus;           /**< Bus serviced by this driver */
>>>>  	const char *name;                   /**< Driver name. */
>>>>  	const char *alias;              /**< Driver alias. */
>>>> +	driver_probe_t *probe;         /**< Probe the device */
>>>> +	driver_remove_t *remove;       /**< Remove/hotplugging the device */
>>>>  };
>>>
>>> If I understand well, this probe function does neither scan nor match.
>>> So it could be named init.
>>
>> Current model is:
>>
>> After scanning for devices and populating bus->device_list,
>> Bus probe does:
>>   `-> bus->match()
>>   `-> rte_driver->probe() for matched driver
>>
>> For PCI drivers, '.probe = rte_eal_pci_probe'.
>>
>> For example, igb_ethdev.c:
>>
>> --->8---
>> static struct eth_driver rte_igb_pmd = {
>>          .pci_drv = {
>>                  .driver = {
>>                          .probe = rte_eal_pci_probe,
>>                          .remove = rte_eal_pci_remove,
>>                  },
>> ...
>> --->8---
>
> Yes
> I'm just having some doubts about the naming "probe" compared to "init".
> And yes I know I was advocating to unify naming to "probe" recently :)
> I would like to be sure it is not confusing for anyone.
> Do you agree that "init" refers to global driver initialization and
> "probe" refers to instantiating a device?

Ok. Makes sense as a standardized way of differentiating 'init' from 
'probe'.

>
> If yes, the comment could be changed from "Probe the device" to
> "Check and instantiate a device".

Now that probe if removed from rte_driver, I think this would no longer 
be valid. [1]

[1] http://dpdk.org/ml/archives/dev/2017-January/054140.html

>
>>> I think the probe (init) and remove ops must be specific to the bus.
>>> We can have them in rte_bus, and as an example, the pci implementation
>>> would call the pci probe and remove ops of rte_pci_driver.
>
> I do not understand clearly what I was saying here :/

:)

>
>> So,
>> ---
>> After scanning for devices (bus->scan()):
>> Bus probe (rte_eal_bus_probe()):
>>   `-> bus->match()
>>   `-> bus->init() - a new fn rte_bus_pci_init()
>
> I suggest the naming bus->probe().
> It is currently implemented in rte_eal_pci_probe_one_driver().
>
>>       -> which calls rte_eal_pci_probe()
>
> Not needed here, this function is converted into the PCI match function.
>
>>       -> and rte_pci_driver->probe()
>
> Yes, bus->probe() makes some processing and calls rte_pci_driver->probe().

I have made some changes on similar lines. Will share them soon. Then we 
can discuss again.

>
>
>> and remove rte_driver probe and remove callbacks because they are now
>> redundant. (they were added in bus patches itself)
>> ---
>>
>> Is the above correct understanding of your statement?
>
> I think we just need to move probe/remove in rte_pci_driver.
>
>> Somehow I don't remember why I didn't do this in first place - it seems
>> to be better option than introducing a rte_driver->probe()/remove()
>> layer. I will change it (and think again why I rejected this idea in
>> first place). Thanks.
>
> Thanks
>