Re: UBI/DVB ioctl conflict?
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Hi, On Monday 08 December 2008 07:20:26 Artem Bityutskiy wrote: > On Sun, 2008-12-07 at 09:58 -0500, Josh Boyer wrote: > > I received a bug report where someone noticed that the UBI ioctls can > > conflict with the dvb subsystem. Looking it over, it seems that both > > subsystems use 'o' as the magic, and do have a set of somewhat > > conflicting sequence numbers as the secondary arg. > > > > Is this a problem? > > Hmm, thanks for noticing. > > I've looked at this, and thankfully it looks like we were lucky and do > not use the same 'ioctl()' numbers, by chance. > > Ioctl number has the following structure: > > bits 0-15: command (or sequence number) > bits 16-29: parameter size > bits 30-31: mode (read, write, etc). > > We have the following overlaps with DVB subsystem: > > #define AUDIO_STOP _IO('o', 1) > #define UBI_IOCRMVOL _IOW('o', 1, int32_t) > > #define AUDIO_PLAY _IO('o', 2) > #define UBI_IOCRSVOL _IOW('o', 2, struct ubi_rsvol_req) > > #define AUDIO_PAUSE _IO('o', 3) > #define UBI_IOCRNVOL _IOW('o', 3, struct ubi_rnvol_req) > > These are fine because parameter sizes are different, and because UBI > uses _IOW and DVB uses _IO, so the mode bits are "01" and "00". > > And: > > #define FE_DISEQC_RECV_SLAVE_REPLY _IOR('o', 64, > struct dvb_diseqc_slave_reply) > #define UBI_IOCATT _IOW('o', 64, struct ubi_attach_req) > > #define FE_DISEQC_SEND_BURST _IO('o', 65) > #define UBI_IOCDET _IOW('o', 65, int32_t) > > are also fine because parameter sizes are different and the mode bits > are different. > > However, we have to be very careful in the future. It seems like DVB > has been in the kernel long before UBI, so this potential conflict > would be my fault. > > Neither DVB nor UBI seem not to be documented in > Documentation/ioctl/ioctl-number.txt. Should we do this? > > P.S. Added Arnd to CC for suggestions, as well as LKML and DVB > maintainers. Correct me if I'm wrong, but doesn't this only matters for devices that would implement both the UBI and DVB API on the same inode ? That would be quite unlikely. Best regards, -- Laurent Pinchart CSE Semaphore Belgium Chaussee de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 F +32 (2) 387 42 75 _______________________________________________ v4l-dvb-maintainer mailing list v4l-dvb-maintainer@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/v4l-dvb-maintainer