Messages in this thread | | | Date | Wed, 29 Dec 1999 20:17:04 +0100 | From | Abramo Bagnara <> | Subject | Re: mmap bug in 2.2.13 (or in documentation) |
| |
James Manning wrote: > > [ Wednesday, December 29, 1999 ] Abramo Bagnara wrote: > > Cause the fall through in do_mmap (around mm/mmap.c:223) all kind of > > file mmap are denied with EACCES if file is not open for reading. > > This is contrary to mmap(2): > > > > Another for me incomprehensible option is that mmap(2) is wrong... can > > someone clarify this? > > I started a small lkml thread about this when I saw the same problem > a couple of months back... since other OS's that I checked had the > same restriction, and since replacing my creat()'s with open(O_RDWR) > wasn't a big deal, I just tagged it as a doc bug... I couldn't think > of a situation where you'd *want/need* to make write-only mmap'd area, > so this seems fine to me (you could even #define your creat() if you > don't want to change the code)
Unfortunately to have write-only mmap'd area it's a way to solve our problem with mmap'd audio devices. To open the file with the right flag permit to us to discriminate at open time the application intention:
O_RDONLY -> Capture O_WRONLY -> Playback O_RDWR -> Full Duplex
It seems natural, isn't it? But mmap force us to not use O_WRONLY, grrr...
Now how we can solve this, avoiding to use 3 different minor for each device (and to use /dev/dsp as it is always used)?
-- Abramo Bagnara mailto:abramo@alsa-project.org
Opera Unica Via Emilia Interna, 140 Phone: +39.0546.656023 48014 Castel Bolognese (RA) - Italy Fax: +39.0546.656023
ALSA project is http://www.alsa-project.org sponsored by SuSE Linux http://www.suse.com
It sounds good!
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |