This is a followup from [1]. 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? * 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 Documentation/driver-api/gpio/driver.rst | 175 ++++++++++++++++++----- drivers/gpio/TODO | 19 +++ drivers/gpio/gpio-pl061.c | 32 +++-- drivers/gpio/gpio-tegra186.c | 32 +++-- drivers/gpio/gpiolib.c | 13 +- drivers/pinctrl/pinctrl-amd.c | 11 +- drivers/pinctrl/pinctrl-apple-gpio.c | 29 ++-- drivers/pinctrl/qcom/pinctrl-msm.c | 53 ++++--- include/linux/gpio/driver.h | 16 +++ include/linux/irq.h | 2 + kernel/irq/debugfs.c | 1 + 11 files changed, 293 insertions(+), 90 deletions(-) -- 2.34.1
