[dpdk-dev] [PATCH v7 6/6] devargs: parse bus info

[Shreyansh Jain]

Hello Gaetan,

On Thursday 06 July 2017 03:30 PM, Gaëtan Rivet wrote:
> On Thu, Jul 06, 2017 at 02:37:16PM +0530, Shreyansh Jain wrote:
>> Hello Gaetan,
>>
>> On Wednesday 05 July 2017 05:25 AM, Gaetan Rivet wrote:
>>> Signed-off-by: Gaetan Rivet <gaetan.rivet at 6wind.com>
>>> ---
>>>   lib/librte_eal/common/eal_common_devargs.c  | 42 ++++++++++++++++++++++++-----
>>>   lib/librte_eal/common/eal_common_vdev.c     |  6 +++--
>>>   lib/librte_eal/common/include/rte_devargs.h |  3 +++
>>>   3 files changed, 42 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/lib/librte_eal/common/eal_common_devargs.c b/lib/librte_eal/common/eal_common_devargs.c
>>> index ffa8ad9..102bd8d 100644
>>> --- a/lib/librte_eal/common/eal_common_devargs.c
>>> +++ b/lib/librte_eal/common/eal_common_devargs.c
>>> @@ -78,12 +78,23 @@ rte_eal_parse_devargs_str(const char *devargs_str,
>>>   	return 0;
>>>   }
>>> +static int
>>> +bus_name_cmp(const struct rte_bus *bus, const void *_name)
>>> +{
>>> +	const char *name = _name;
>>> +
>>> +	return strncmp(bus->name, name,
>>> +		       strlen(bus->name));
>>
>> Trivial: Any specific reason why this is split across multiple lines even
>> though it is less than 80 chars in total?
>>
> 
> Not really, it's only a matter of taste.
> If is mostly to hightlight that we are limiting the comparison to
> bus->name length, by putting it on its own line.

Ok. I am ok with this.

> 
>>> +}
>>> +
>>>   /* store a whitelist parameter for later parsing */
>>>   int
>>>   rte_eal_devargs_add(enum rte_devtype devtype, const char *devargs_str)
>>>   {
>>>   	struct rte_devargs *devargs = NULL;
>>> -	char *buf = NULL;
>>> +	struct rte_bus *bus = NULL;
>>> +	char *dev = NULL;
>>> +	const char *devname;
>>>   	int ret;
>>>   	/* use malloc instead of rte_malloc as it's called early at init */
>>> @@ -94,34 +105,51 @@ rte_eal_devargs_add(enum rte_devtype devtype, const char *devargs_str)
>>>   	memset(devargs, 0, sizeof(*devargs));
>>>   	devargs->type = devtype;
>>> -	if (rte_eal_parse_devargs_str(devargs_str, &buf, &devargs->args))
>>> +	if (rte_eal_parse_devargs_str(devargs_str, &dev, &devargs->args))
>>
>> A very basic (and possibly incorrect) question:
>>
>> here, for example "'net_pcap0,rx_pcap=input.pcap,tx_pcap=output.pcap'" was
>> passed to application, which would mean;
>>
>> dev = "net_pcap0" (name of the device)
>> devargs = "rx_pcap=input.pcap,tx_pcap=output.pcap"
>>
>>>   		goto fail;
>>> +	devname = dev;
>>> +	do {
>>> +		bus = rte_bus_find(bus, bus_name_cmp, dev);
>>> +		if (bus == NULL)
>>> +			break;
>>> +		devname = dev + strlen(bus->name) + 1;
>>
>> Assuming "vdev" bus:
>>                        "net_pcap0"
>>                              |
>> devname points here --------' (4+1) chars from start of "net_pcap0".
>> Is that the expectation?
>>
> 
> Yes :)
> Well, actually, almost. The lines
> 
>>> +		bus = rte_bus_find(bus, bus_name_cmp, dev);
>>> +		if (bus == NULL)
>>> +			break;
> 
> Mean that at this point, we would already have broken out of the loop.
> But to continue with your example, assuming that we have a bus that
> is named "net_p":
> 
>> Probably I am missing something here (maybe the input already has a bus
>> name.)
>>
>> Or, if this is not the case, then we will have to change the test
>> application (test_devargs.c) which passes such strings to
>> "rte_eal_devargs_add".
>>
>>> +		if (rte_bus_find_by_device_name(devname) == bus)
>>
>> Obviously, if my assumption is correct, this fails. Or, maybe I am
>> completely off the mark.
>>
> 
> It should not be necessary to update the tests (yet).
> This bit of code tries to recognize bus names at the start of the
> declaration. However, some device names might be ambiguous and start
> like bus names for any reason. Device names have no specification beside
> not having commas within, bus names have no specification at all.
> 
> Thus, we first try here to recognize a bus name within dev, but we do
> not stop here. We also verify afterward that the resulting device would
> be correct, and that its bus handler is actually the same as the bus we
> first recognized.
> 
> In your example, the line
> 
> 
>>> +        if (rte_bus_find_by_device_name(devname) == bus)
> 
> Fails, as the device is incorrect and rte_bus_find_by_device_name
> returns NULL as no bus is able to handle a device named
> 
>> "cap0,rx_pcap=input.pcap,tx_pcap=output.pcap"
> 
> Considering this, we should break from this loop with no recognized bus.
> As such, we enter afterward in the branch:
> 
>>> +			break;
>>> +		devname = dev;
> 
> Note here that devname is set back to the start of dev.
> 
>>> +	} while (1);
>>> +	if (bus == NULL) {
>>> +		bus = rte_bus_find_by_device_name(devname);
> 
> Which will try to recognize a bus from the device name ("net_pcap0"),
> which should succeed in recognizing vdev.
> 
> It is a little contrived, but I wanted this parsing to both be flexible
> and perform as many checks as possible.
> 
> I am developing a new bus that have a high probability of name conflicts
> with other device names, so I am extra careful on this side.

Ok. I completely missed this logic.
Thanks.

> 
>>> +		if (bus == NULL) {
>>> +			fprintf(stderr, "ERROR: failed to parse bus info from device declaration\n");
>>> +			goto fail;
>>> +		}
>>> +	}
>>> +	devargs->bus = bus;
>>    >   	switch (devargs->type) {
>>>   	case RTE_DEVTYPE_WHITELISTED_PCI:
>>>   	case RTE_DEVTYPE_BLACKLISTED_PCI:
>>>   		/* try to parse pci identifier */
>>> -		if (eal_parse_pci_BDF(buf, &devargs->pci.addr) != 0 &&
>>> -		    eal_parse_pci_DomBDF(buf, &devargs->pci.addr) != 0)
>>> +		if (bus->parse(devname, &devargs->pci.addr) != 0)
>>>   			goto fail;
>>>   		break;
>>>   	case RTE_DEVTYPE_VIRTUAL:
>>>   		/* save driver name */
>>>   		ret = snprintf(devargs->virt.drv_name,
>>> -			       sizeof(devargs->virt.drv_name), "%s", buf);
>>> +			       sizeof(devargs->virt.drv_name), "%s", devname);
>>>   		if (ret < 0 || ret >= (int)sizeof(devargs->virt.drv_name))
>>>   			goto fail;
>>>   		break;
>>>   	}
>>
>> I think all this will change in the devargs series.
>>
> 
> Indeed :)
> 
>>> -	free(buf);
>>> +	free(dev);
>>>   	TAILQ_INSERT_TAIL(&devargs_list, devargs, next);
>>>   	return 0;
>>>   fail:
>>> -	free(buf);
>>> +	free(dev);
>>>   	if (devargs) {
>>>   		free(devargs->args);
>>>   		free(devargs);
>>> diff --git a/lib/librte_eal/common/eal_common_vdev.c b/lib/librte_eal/common/eal_common_vdev.c
>>> index 6ecd1b5..8fd1ef7 100644
>>> --- a/lib/librte_eal/common/eal_common_vdev.c
>>> +++ b/lib/librte_eal/common/eal_common_vdev.c
>>> @@ -177,6 +177,7 @@ alloc_devargs(const char *name, const char *args)
>>>   		return NULL;
>>>   	devargs->type = RTE_DEVTYPE_VIRTUAL;
>>> +	devargs->bus = rte_bus_find_by_name("vdev");
>>>   	if (args)
>>>   		devargs->args = strdup(args);
>>> @@ -289,12 +290,13 @@ vdev_scan(void)
>>>   {
>>>   	struct rte_vdev_device *dev;
>>>   	struct rte_devargs *devargs;
>>> +	struct rte_bus *vbus;
>>>   	/* for virtual devices we scan the devargs_list populated via cmdline */
>>> -
>>> +	vbus = rte_bus_find_by_name("vdev");
>>>   	TAILQ_FOREACH(devargs, &devargs_list, next) {
>>> -		if (devargs->type != RTE_DEVTYPE_VIRTUAL)
>>> +		if (devargs->bus != vbus)
>>>   			continue;
>>>   		dev = find_vdev(devargs->virt.drv_name);
>>> diff --git a/lib/librte_eal/common/include/rte_devargs.h b/lib/librte_eal/common/include/rte_devargs.h
>>> index 88120a1..1f50a24 100644
>>> --- a/lib/librte_eal/common/include/rte_devargs.h
>>> +++ b/lib/librte_eal/common/include/rte_devargs.h
>>> @@ -51,6 +51,7 @@ extern "C" {
>>>   #include <stdio.h>
>>>   #include <sys/queue.h>
>>>   #include <rte_pci.h>
>>> +#include <rte_bus.h>
>>>   /**
>>>    * Type of generic device
>>> @@ -89,6 +90,8 @@ struct rte_devargs {
>>>   			char drv_name[32];
>>>   		} virt;
>>>   	};
>>> +	/** Bus handle for the device. */
>>> +	struct rte_bus *bus;
>>>   	/** Arguments string as given by user or "" for no argument. */
>>>   	char *args;
>>>   };
>>>
>> -
>> Shreyansh
> 

And, for this patch as well:

Acked-by: Shreyansh Jain <shreyansh.jain at nxp.com>