On Tue, Apr 5, 2022 at 3:55 PM Marc Zyngier <maz@xxxxxxxxxx> wrote: > 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? > > * From v1 [1]: > - pl061 and AMD drivers converted > - New helpers to keep the changes small > - New warning for non-converted drivers > - Documentation and TODO updates > > [1] https://lore.kernel.org/r/20220223154405.54912-1-maz@xxxxxxxxxx > > Marc Zyngier (10): > gpio: Don't fiddle with irqchips marked as immutable > gpio: Expose the gpiochip_irq_re[ql]res helpers > gpio: Add helpers to ease the transition towards immutable irq_chip > gpio: tegra186: Make the irqchip immutable > gpio: pl061: Make the irqchip immutable > pinctrl: apple-gpio: Make the irqchip immutable > pinctrl: msmgpio: Make the irqchip immutable > pinctrl: amd: Make the irqchip immutable > gpio: Update TODO to mention immutable irq_chip structures > Documentation: Update the recommended pattern for GPIO irqchips Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx> Yours, Linus Walleij
