On Fri, 22 Apr 2022 22:24:22 +0100, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Tue, Apr 19, 2022 at 4:19 PM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > > This is a followup from [2]. > > > > I recently realised that the gpiolib play ugly tricks on the > > unsuspecting irq_chip structures by patching the callbacks. > > > > Not only this breaks when an irq_chip structure is made const (which > > really should be the default case), but it also forces this structure > > to be copied at nauseam for each instance of the GPIO block, which is > > a waste of memory. > > > > My current approach is to add a new irq_chip flag (IRQCHIP_IMMUTABLE) > > which does what it says on the tin: don't you dare writing to them. > > Gpiolib is further updated not to install its own callbacks, and it > > becomes the responsibility of the driver to call into the gpiolib when > > required. This is similar to what we do for other subsystems such as > > PCI-MSI. > > > > 5 drivers are updated to this new model: M1, QC, Tegra, pl061 and AMD > > (as I actively use them) keeping a single irq_chip structure, marking > > it const, and exposing the new flag. > > > > Nothing breaks, the volume of change is small, the memory usage goes > > down and we have fewer callbacks that can be used as attack vectors. > > What's not to love? > > > > Since there wasn't any objection in the previous round of review, I'm > > going to take this series into -next to see if anything breaks at > > scale. > > The series: > Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > > Bartosz: if you're happy with this can you apply it to an immutable branch > from v5.18-rc1 and merge that into the GPIO for-next and then I can also > pull that into pinctrl? For what it is worth, I've pushed this branch into irqchip-next. You can pick it up from: https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/gpio-immutable but I can also drop it from the irqchip tree. Just let me know. M. -- Without deviation from the norm, progress is not possible.
