On Mon, Nov 02, 2015 at 11:31:16AM +0100, Johan Hovold wrote: > On Thu, Oct 22, 2015 at 10:32:25AM +0200, Linus Walleij wrote: > > + /* > > + * The "dev" member of gpiochip is the parent, and the actual > > + * device is named "device" for historical reasons. > > + * > > + * We memset the struct to zero to avoid reentrance issues. > > + */ > > + memset(&chip->device, 0, sizeof(chip->device)); > This is an indication of a larger problem. > First of all, you must never register the same device structure twice. Well, you can unregister and reregister (and it is reasonable practice to make sure that the struct isn't full of noise) - we usually allocate things out of kzalloc(). > And the larger problem is: With the current interface where a struct > gpio_chip is passed and registered, how would you prevent the device > from going away while in use? Hrm, indeed. Why aren't there complaints about a missing release function there? > You grab a reference to the chip->device when opening the node (in a > later patch), but it is not used to manage the life time of struct > gpio_chip. That's a slightly separate thing and even with a different implementation of the file we still have to assume that the driver core might hold a reference to the device for longer (for example as a result of sysfs interactions).
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