On Friday, March 15, 2013 9:16 AM, Greg Kroah-Hartman wrote: > On Fri, Mar 15, 2013 at 01:15:33PM +0000, Ian Abbott wrote: >> Change the `attached` member of `struct comedi_device` to a 1-bit >> bit-field of type `bool`. Change assigned values to `true` and `false` >> and replace or remove comparison operations with simple boolean tests. >> >> We'll put some extra bit-fields in the gap later to save space. >> >> Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx> <snip> >> + bool attached:1; > > I'm not objecting to this, but for some reason I thought that bit fields > could only be a 'unsigned int'. Or am I just used to C88 or some such > really old spec of the C standard? I'm not sure about this either. Using bit fields with a bool is found in the kernel but it's not very common. A quick grep shows these: drivers/block/DAC960.h drivers/md/dm-cache-metadata.c drivers/md/dm-cache-policy-cleaner.c drivers/md/dm-cache-policy-mq.c drivers/md/dm-cache-target.c drivers/md/dm-thin-metadata.c drivers/md/dm-thin.c drivers/md/persistent-data/dm-bitset.h drivers/md/persistent-data/dm-block-manager.c drivers/md/persistent-data/dm-space-map-common.h drivers/pinctrl/pinctrl-nomadik.h drivers/scsi/BusLogic.h drivers/scsi/sr.h drivers/target/iscsi/iscsi_target_core.h drivers/usb/host/ehci.h drivers/video/omap2/dss/dispc.c fs/cifs/cifsglob.h fs/fuse/fuse_i.h include/acpi/acpi_bus.h include/linux/device-mapper.h include/linux/pm.h include/linux/pm_wakeup.h include/linux/sysfs.h include/target/target_core_base.h kernel/printk.c net/dccp/feat.h sound/pci/hda/hda_local.h I guess the real question is, what's the underlying type of a bool? It must be an unsigned "something" or the compiler would complain. And does assigning a bit field to the bool actually save any space? <linux/types.h> typedef _Bool bool; _Bool is a standard type in C99 I found this: http://gcc.gnu.org/ml/gcc-patches/2000-10/msg01127.html But honestly still don't know what a _Bool is... :-) Regards, Hartley _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
