[dpdk-dev] [PATCH v8 03/10] drivers: relax dependency order

[Parav Pandit]

Hi Bruce,

> From: Bruce Richardson <bruce.richardson at intel.com>
> Sent: Friday, July 24, 2020 4:37 PM
> 
> On Thu, Jul 23, 2020 at 11:09:03PM +0300, Parav Pandit wrote:
> > From: Thomas Monjalon <thomas at monjalon.net>
> >
> > Drivers dependencies are evaluated in the order defined per their
> > parent directory (also called class).
> > This strict ordering prevent from having 2 different drivers of the
> > same class with different dependencies ordering.
> > This problem occurs if drivers/common/mlx5 depends on drivers/bus/pci,
> > while drivers/bus/dpaa depends on drivers/common/dpaax.
> > Having a strict ordering between directories bus and common is too
> > much restrictive.
> >
> > That's why it is made possible to have a more fine-grain directory
> > list, adding a driver sub-directory in the list.
> > In this case, the isolated driver must be removed from its class list,
> > and added directly in drivers/meson.build.
> > Also, the per-class variables must be duplicated in the isolated
> > driver, because the call "subdir(class)" is skipped in the isolated driver case.
> >
> > Signed-off-by: Thomas Monjalon <thomas at monjalon.net>
> 
> The commit log above has some strange word-wrapping, and occasionally
> strange phrasing. I think it could be slightly reworded, perhaps as:
> 
I updated the commit log as you suggested below along with RB, ack tag.
Thank you.

>   Drivers dependencies are evaluated in the order defined per their parent
>   directory (also called class). This strict ordering prevents from us
>   from having pairs of drivers from two classes with different dependency
>   ordering. For example, if the mlx5 common code depends on the pci bus
>   driver, while the dpaax common code is itself a dependency of the dpaa
>   bus driver.  Having a strict ordering between directories bus and common
>   is too restrictive, as processing either common drivers or bus drivers
>   first leads us to missing dependencies in this scenario.
> 
>   This patch makes it possible to have a more fine-grain directory list,
>   adding a specific driver sub-directory in the top-level drivers
>   subdirectory list. In this case, the isolated driver must also be removed
>   from its class list, and the per-class variables must be duplicated in
>   the isolated driver, because the call "subdir(class)" is skipped in the
>   isolated driver case.
> 
> 
> Apart from that, I think this is a good idea to give us some flexibility in
> managing driver ordering which should help other drivers too - perhaps QAT?
> Ideally, though, I'd like if we can limit the flexible ordering to *only* common
> code, in which case we could move the per-class variables for common to the
> top-level to prevent duplication, and maybe even get rid of
> common/meson.build completely. That, however, will depend on how much
> this feature gets used and by whom.
> 
> Therefore:
> Review-by: Bruce Richardson <bruce.richardson at intel.com>
> Acked-by: Bruce Richardson <bruce.richardson at intel.com>