The Linux operating system (OS) is evolving rapidly to improve
performance and to provide new features. This evolution, however,
makes it difficult to maintain platform-specific code such as device
drivers. Indeed, an evolution in a driver support library often
triggers the need for multiple collateral evolutions in dependent
device drivers, to bring the drivers up to date with the new library
API. Currently, collateral evolutions are mostly done manually.
The large number of drivers, however, implies that this approach
is time-consuming and unreliable, leading to subtle errors when
modifications are not done consistently. Moreover, as these collateral
evolutions are often poorly documented, the resulting maintenance
is difficult and costly, frequently introducing errors. If a driver
maintainer becomes unavailable, the driver quickly falls behind
the rest of the OS.

In this project, we propose a language-based approach to address
the problem of collateral evolution in drivers. Specifically, we
are developing the development environment, Coccinelle, that provides
a transformation language for precisely expressing collateral
evolutions and an interactive transformation tool for applying
them. The key idea of Coccinelle is to shift the burden of collateral
evolution from the driver maintainer to the OS developer who performs
the original OS evolution, and who thus understands this evolution
best. In our vision, the OS developer first uses the Coccinelle
transformation language to write a semantic patch describing the
required collateral evolution in device drivers and then uses the
Coccinelle transformation tool to validate the semantic patch on
the drivers in the Linux source distribution. When he has confidence
in the correctness of the semantic patch, he distributes it for
use by the maintainers of other drivers. Overall, Coccinelle will
provide a means for formally documenting collateral evolutions and
for easing the application of these evolutions to driver code.