[ECOS] I/O driver lookup handler: read/write mode

["Masaki Sawanobori" <masaki at zentek dot com>]

Hello,

I am implementing a simple flash memory file system in the framework of eCos
I/O device driver model and C language libc stdio module so the user can
access a file using fopen() as follows.

    FILE *fp = fopen("/dev/flash0/filename", "r");
    FILE *fp = fopen("/flash0/filename", "w");

The problem is that the second paramter(read/write mode) of fopen() is not
passed down to a "lookup" device driver handler(via the cyg_io_lookup
function). The "lookup" handler has no way of returning a correct
return/error value without knowing whether a file(existing or non-existing)
is for read or write.

I would not like to resort to a workaround of adding a read/write mode
specifier as part of a filename parameter like "/nvram/filename/w" or
"/nvram/filename/r" or "/nvramR"/filename" or "/nvramW/filename".  This
would be redundant for fopen().

Is there any other workaround or a solution for this situation? Am I missing
something ?

Here is another wish about I/O device driver handlers. There is no "close"
handler.  I could use a "close" handler since it seems to be a right place
to free memory allocated in my "lookup" handler.

-- Masaki S.