Re: Git: new feature suggestion

[Joao Pinto <Joao.Pinto@synopsys.com>]

Às 7:16 PM de 1/19/2017, Linus Torvalds escreveu:
> On Thu, Jan 19, 2017 at 10:54 AM, Joao Pinto <Joao.Pinto@synopsys.com> wrote:
>>
>> I am currently facing some challenges in one of Linux subsystems where a rename
>> of a set of folders and files would be the perfect scenario for future
>> development, but the suggestion is not accepted, not because it's not correct,
>> but because it makes the maintainer life harder in backporting bug fixes and new
>> features to older kernel versions and because it is not easy to follow the
>> renamed file/folder history from the kernel.org history logs.
> 
> Honestly, that's less of a git issue, and more of a "patch will not
> apply across versions" issue.
> 
> No amount of rename detection will ever fix that, simply because the
> rename hadn't even _happened_ in the old versions that things get
> backported to.
> 
> ("git cherry-pick" can do a merge resolution and thus do "backwards"
> renaming too, so tooling can definitely help, but it still ends up
> meaning that even trivial patches are no longer the _same_ trivial
> patch across versions).
> 
> So renaming things increases maintainer workloads in those situations
> regardless of any tooling issues.
> 
> (You may also be referring to the mellanox mess, where this issue is
> very much exacerbated by having different groups working on the same
> thing, and maintainers having very much a "I will not take _anything_
> from any of the groups that makes my life more complicated" model,
> because those groups fucked up so much in the past).
> 
> In other words, quite often issues are about workflows rather than
> tools. The networking layer probably has more of this, because David
> actually does the backports himself, so he _really_ doesn't want to
> complicate things.

I totally understand David' side! Synopsys is a well-known IP Vendor, and for a
long time its focus was the IP only. Knowadays the strategy has changed and
Synopsys is very keen to help in Open Source, namelly Linux, developing the
drivers for new IP Cores and participating in the improvement of existing ones.
I am part of the team that has that job.

In USB and PCI subystems developers created common Synopsys drivers (focused on
the HW IP) and so today they are massively used by all the SoC that use Synopsys
IP.

In the network subsystem, there are some drivers that target the same IP but
were made by different companies. stmmac is an excelent driver for Synopsys MAC
10/100/1000/QOS IPs, but there was another driver made by AXIS driver that also
targeted the QOS IP. We detected that issue and merged the AXIS specific driver
ops to stmmac, and nowadays, AXIS uses stmmac. So less drivers to maintain!

The idea that was rejected consisted of renaming stmicro/stmmac to dwc/stmmac
and to have dwc (designware controllers) as the official driver spot for
Synopsys Ethernet IPs.
There is another example of duplication, which is AMD' and Samsung' XGMAC
driver, targeting the same Synopsys XGMAC IP.

I am giving this examples because although the refactor adds work for
backporting, it reduces the maintenance since we would have less duplicated
drivers as we have today.

Thanks,
Joao


>                Linus
>