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

[Jonathan Larmour <jlarmour@cygnus.co.uk>]

Masaki Sawanobori wrote:
> 
> 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");

Gosh. That's good. Are you considering contributing it back? 
 
> 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().

Quite, although it wouldn't need to be passed that way for fopen, only
cyg_io_lookup.

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

Using cyg_io_get_config() after the cyg_io_lookup() would seem a better
approach.
 
> 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.

This is true. We intend to do something about that in the eCos
implementation of EL/IX, but that may take some time. We intend to do
pluggable filesystems as well, so everything should get sorted out
eventually.

Jifl
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