Deos-headers package proposal

Single Header, Multiple Component (SHMC)

Several whiles ago the driver team needed a way to provide a single header file from multiple drivers.

The way it works:

• Example: i2c-ioctl.h
  • A header file containing fairly common ioctl request codes for I2C drivers.
  • All of our I2C drivers have the same request codes for the same function.
  • Portability, reuse, savings.
• A component, vfile-common-headers, is where the i2c-ioctl.h header file is stored, maintained, PCRed, and importantly, where it is delivered from.
  • An I2C driver svn:externs the i2c-ioctl.h header so that it can provide the ioctl requests.
  • If this I2C driver is verified, the verification of the svn:externed i2c-ioctl.h header occurs as does verification of any other svn:extern.

All is good.

stdio.h

A DVMS improvement proposal would like to add the stdio FILE APIs.

• You know: fopen, fread, fwrite, ftell, fseek, fclose, ...
  • These naturally contain a RAM buffer which improves performance by reducing calls to media for small read/write requests.

The problem: stdio.h, where the prototypes of these functions belong, is owned/delivered by ANSI.

deos-headers package proposal

Solution proposed:

• Similar to vfile-common-headers, create a SHMC component called deos-headers (?).
• But it's not quite as simple as the I2C example above.
  • stdio.h has DEOSBASEAPI/DEOSABIAPI function prototypes in it.
  • ANSI provides the implementation of functions that are in its delivered stdio.h.
    • vfile would like to provide the implementation of functions that aren't in ANSI's stdio.h.
    • ANSI shouldn't have to be bothered with stdio.h content that it doesn't provide or care about.
      • In fact, adding the stdio FILE APIs to ANSI's stdio.h would likely cause an issue with our exported symbols checker.

Coming up for air. Where to go from here?

Proposal:

1. Rename ANSI stdio.h to ansi-stdio.h.
2. ANSI delivers ansi-stdio.h to DI_DESK_INCLUDE_PROJECT (/desk/include/ansi)
3. vfile creates and delivers vfile-stdio.h to DI_DESK_INCLUDE_PROJECT (/desk/include/vfile)
4. Add stdio.h to deos-headers component, content of:

#include <ansi-stdio.h>
#include <vfile-stdio.h>

1. Users would include, as usual, <stdio.h>

Problems:

1. The deos-headers stdio.h assumes ANSI and vfile are delivered to a customer.
   • Someone suggested the /desk/include/stdio.h could be generated by a postinstall script which would include all stdio-*.h found in the installation media.

errno.h

We'd all like one place to put errno values.

• We'd all like to not have to unrelease ANSI to accomplish this.
• ANSI only owns this because it provides strerror_r.
  • A proposal for strerror_r was to include a file that is the error strings which would be parsed at start-up so that strerror_r could index into the file to find the proper string.

other.h?

I'm sure there are other headers out there that could use some attention.