(added linux-media mail-list) Hello to all On Wed, 2009-01-21 at 21:44 +0100, Thierry Merle wrote: > Hi Douglas, > Douglas Schilling Landgraf a écrit : > > Hello friends, > > > > Since you sent patches to linux-media for usb_make_path changes, I > > would like to make a question for you. Should we check for > > return of usb_make_path as a good programming practice? > > > > static inline int usb_make_path(struct usb_device *dev, char *buf, > > size_t size) > > > > I didn't see this check in your patches. > > > I saw that the return code was checked in some other v4l sources, but I preferred to ignore the return value like done in many other drivers (see http://lxr.falinux.com/ident?i=usb_make_path) > I know it is bad but for failing this function fails if the buffer is to small to copy the complete usb path. > Nevertheless it uses snprintf that truncates safely the string if needed. > What to do if this function fails? I did not see anything better, so ignoring the return code seemed to be the best. usb_make_path returns -1 if sizeof buffer is smaler than path (no device or hardware troubles). Bus_info is 32 byte and usb path looks like: "usb-%s-%s", dev->bus->bus_name, dev->devpath (from usb.h). I failed trying to find size of bus_name, but maximum size of dev->devpath is 16 chars. So, i'm confused about two things: - as this information goes to userspace, will userpace feel bad that trucated string will be delivered? And do v4l-subsystem care enough to provide complete usb-path? - will it happened one day that usb_make_path returns -1 and we care? I don't have ideas about first thing. In case we care to provide full usb-path - may be check for returned value should be placed, print message and ask user, for example: "usb_make_path error! Please send message to linux-media maillist". In case of many reports size of bus_info[32] can be increased. By other side, if this all is really important? It's right that ignoring returned value is safe. -- Best regards, Klimov Alexey -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
