Re: [dpdk-dev] [PATCH v2] eal/devargs: add option to supply PCI dev args

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

On Mon, Jul 16, 2018 at 12:25:29AM +0200, Thomas Monjalon wrote:
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>
> 10/07/2018 12:19, Pavan Nikhilesh:
> > Hi Gaëtan,Ferruh,
> >
> > On Wed, Jun 27, 2018 at 11:57:36AM +0200, Gaëtan Rivet wrote:
> > > On Wed, Jun 27, 2018 at 02:25:30PM +0530, Pavan Nikhilesh wrote:
> > > > Hi Gaëtan,
> > > >
> > > > On Wed, Jun 27, 2018 at 10:39:59AM +0200, Gaëtan Rivet wrote:
> > > > > Hi Ferruh, Pavan,
> > > > >
> > > > > sorry for the delay,
> > > > >
> > > > > On Tue, Jun 26, 2018 at 04:40:21PM +0100, Ferruh Yigit wrote:
> > > > > > On 6/26/2018 1:48 PM, Shahaf Shuler wrote:
> > > > > > > Hi Pavan,
> > > > > > >
> > > > > > > Friday, June 15, 2018 7:44 AM, Pavan Nikhilesh:
> > > > > > >> Subject: [dpdk-dev] [PATCH v2] eal/devargs: add option to supply PCI dev
> > > > > > >> args
> > > > > > >>
> > > > > > >> Currently, the only way of supplying device argument to a pci device is to
> > > > > > >> whitelist it i.e. -w 000X:00:0X.0,self_test=1. This is not a very feasible method
> > > > > > >> as whitelisting a device has its own side effects i.e only the whitelisted pci
> > > > > > >> devices are probed.
> > > > > > >>
> > > > > > >> Add a new eal command line option --pci-args to pass device args without the
> > > > > > >> need to whitelist the devices.
> > > > > > >>            --pci-args 000X:00:0X.0,self_test=1
> > > > > > >>
> > > > > > >> Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> > > > > > >
> > > > > > > Tested-by: Shahaf Shuler <shahafs@mellanox.com>
> > > > > > >
> > > > > > > It seems to work.
> > > > > > > Please see small comments below
> > > > > >
> > > > > > Isn't this conflict with Gaetan's devarg work which has wider scope?
> > > > > >
> > > > >
> > > > > Indeed it does.
> > > > >
> > > > > Pavan, I have submitted a new version of a series adding generic kvargs
> > > > > to several layers (bus, class, driver).
> > > > >
> > > > > It does cover this exact use-case.
> > > > >
> > > > > However, while writing it, I wasn't able to find PCI bus specific
> > > > > parameters, that could showcase the functionality.
> > > >
> > > > The idea of the patch is to avoid whitelising a device when we want to
> > > > supply kvargs to it, I tried mapping it to devargs rework patchset but couldn't
> > > > do it at a glance. For example, the following patch[1] reads kvargs through
> > > > whitelisting which should be avoided.
> > > >
> > > > [1]http://patches.dpdk.org/patch/41223/
> > > >
> > >
> > > I see.
> > >
> > > Actually, your use-case won't be covered by the devargs rework.
> > >
> > > I am still dumbfounded by how this blacklist/whitelist mode stuff is
> > > kept against all odds. But that's not the time to deal with it.
> > >
> > > The issue is that the two features "declaring a device" and
> > > "configuring a bus" are currently awkwardly merged. You are piling stuff
> > > on the "declaring a device" part to enhance the "configuring a bus"
> > > feature.
> >
> > The feature is very much needed to avoid polluting the cmdline args when we are
> > trying to configure a device at probe (for now).
> >
> > >
> > > Instead of going this way, I would advise to separate the two features.
> > >
> > > If buses could be configured with a generic EAL option
> > > "--blacklist=pci,vdev" for example, then you could provide devargs as
> > > much as you want, the buses themselves would stay properly configured.
> > >
> > > This means removing devargs policy, device types and rewriting bus logic
> > > about it.
> >
> > I think this can be done as a future work and is not in the scope of this
> > patch.
> >
> > @Ferruh,
> > As Gaëtan mentioned this patch is not related to devargs rework can we make
> > some forward progress.
>
> No, we should not add a new parameter just to fix one use case for one bus.
> The work of Gaetan is opening the door to a generic syntax which can be
> used for device matching (like for whitelisting), or for settings
> (what you need) of any bus, any device class or any driver.
> We can discuss about which option to add for generic device settings,
> and whether or not it should be mixed with whitelisting,
> but please let's work on a generic solution.

Ok, I guess this can be taken up once Gaëtan devarsg patches are completely
merged. If we split the work into a smaller list we could load balance the
work and work towards 18.11?.

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