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Re: I/O driver lookup handler: read/write mode
- To: Masaki Sawanobori <masaki at zentek dot com>
- Subject: Re: [ECOS] I/O driver lookup handler: read/write mode
- From: Jonathan Larmour <jlarmour at cygnus dot co dot uk>
- Date: Tue, 30 Nov 1999 15:36:01 +0000
- CC: ecos-discuss at sourceware dot cygnus dot com
- Organization: Cygnus Solutions
- References: <062c01bf3b22$2a8be000$437201aa@atlantis7>
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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