Re: [Xen-devel] [RFC PATCH v1 2/7] iommu/arm: ipmmu-vmsa: Add Xen changes for main driver

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

Hi, Stefano, Julien.

On Fri, Aug 25, 2017 at 11:06 PM, Stefano Stabellini
<sstabellini@xxxxxxxxxx> wrote:
> On Wed, 23 Aug 2017, Julien Grall wrote:
>> Hi Oleksandr,
>>
>> On 21/08/17 16:53, Oleksandr Tyshchenko wrote:
>> > On Thu, Aug 10, 2017 at 6:13 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>> > > On 10/08/17 15:27, Oleksandr Tyshchenko wrote:
>> > > > I would like to clarify what need to be done from my side.
>> > > > Should I wait for the missing things reach upsteam and then rebase on
>> > > > the mainline driver?
>> > > > Or should I rewrite this driver without following Linux?
>> > >
>> > >
>> > > I don't have a clear answer here. As I said, we need to weight pros and
>> > > cons
>> > > to use Linux driver over our own.
>> > >
>> > > At the moment, you are using a BSP driver which has more features but
>> > > modified quite a lot. We don't even know when this is going to be merged
>> > > in
>> > > Linux.
>> > >
>> > > Keeping code close to Linux requires some hacks that are acceptable if 
>> > > you
>> > > can benefits from the community (bug fix, review...). As the driver is
>> > > taken
>> > > from the BSP, we don't know if the code will stay in the current form nor
>> > > be
>> > > able to get bug fix.
>> >
>> > I got it. Completely agree with you.
>> > But, we need to choose which direction we should follow. We have 3
>> > options at the moment
>> > and I am OK with each of them:
>> > 1. direct port from BSP (current implementation).
>> > 2. direct port from mainline Linux (when it has required support).
>> > 3. new driver based on BSP/Linux and contains only relevant to Xen things.
>> >
>> > I am starting to think that options 2 or 3 (+) would be more suitable.
>> > What do you think?
>>
>> The option 2 rely on the changes to be merged in Linux. If I understand
>> correctly, we don't have any timeline for this.
>>
>> So I would lean towards option 3 to get a support in Xen.
>>
>> Stefano, do you have any opinion?
>
> I agree with Julien. Option 3 is the way to go. There is only a benefit
> in staying close to Linux if their driver is in good state, fully
> featured, and well-maintained. And we certainly don't want to block your
> work on waiting for somebody else who might or might nor merge his
> changes in Linux. In this case, option 3 is best.
Thank you for your suggestions.

> I warn you, you might
> have to maintain this driver in Xen going forward though :-)
Why not :-)

-- 
Regards,

Oleksandr Tyshchenko

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