| Date | Fri, 29 Jan 2010 16:40:47 -0500 | From | Jeff Garzik <> | Subject | Re: [PATCH 00/68] ide2libata |
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On 01/29/2010 11:03 AM, Bartlomiej Zolnierkiewicz wrote: > Hi, > > Here is a patchset (on top of atang-v3.1 tree) applying "out-of-the-box" > thinking to duplicated libata PATA and IDE subsystem host driver sets. > Namely, it modifies IDE API slightly to match libata's one more, adds > a tiny source-code level translation layer (ide2libata.h header file > which consists of only 17 lines of code) and then converts host drivers > to use shared source code for low-level operations (all drivers have > been carefully audited during porting to minimize the probability of > adding regressions accidentally). As an end result it is much easier > to maintain both driver sets (differences between 'new'/'old' drivers > are now apparent and there is no longer a need to manually back-port > many classes of bugfixes) and over 2500 LOC are gone.
Interesting.
I'm fine with applying patches 2-5, but I am definitely interested to hear what others think about this. Clearly, LOC is reduced, but that's not the only factor in code maintenance.
With regards to libata and old-IDE, I have always thought the ideal scenario was to leave old-IDE in bugfix-only mode, with next-to-no API or driver churn besides that which is absolutely required for the fix.
En masse backporting bug fixes is what's known as a one-time cost. Once the majority of libata PATA drivers reach bugfix and feature parity, the need for code sharing is reduced greatly.
The ide2libata proposal creates on-going costs, not just a one-time cost, because the old-IDE drivers will have -increased- potential for problems when a libata PATA driver is modified. Such is the -cost- of heavily intertwined code sharing. A single header change implies that two, not one, drivers might break. That weakens the "leave it alone" stability promise of old-IDE.
Waiting for other comments... this patchset is not an onerous burden to libata, but I think it creates nasty cross-tree issues, potentially perturbing old-IDE.
Jeff
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