1 files changed, 36 insertions, 49 deletions
diff --git a/drivers/gpio/TODO b/drivers/gpio/TODO
index e560e45e84f8..0229fa79499e 100644
--- a/drivers/gpio/TODO
+++ b/drivers/gpio/TODO
@@ -129,58 +129,9 @@ GPIOLIB irqchip
 The GPIOLIB irqchip is a helper irqchip for "simple cases" that should
 try to cover any generic kind of irqchip cascaded from a GPIO.
 
-- Convert all the GPIOLIB_IRQCHIP users to pass an irqchip template,
-  parent and flags before calling [devm_]gpiochip_add[_data]().
-  Currently we set up the irqchip after setting up the gpiochip
-  using gpiochip_irqchip_add() and gpiochip_set_[chained|nested]_irqchip().
-  This is too complex, so convert all users over to just set up
-  the irqchip before registering the gpio_chip, typical example:
-
-  /* Typical state container with dynamic irqchip */
-  struct my_gpio {
-      struct gpio_chip gc;
-      struct irq_chip irq;
-  };
-
-  int irq; /* from platform etc */
-  struct my_gpio *g;
-  struct gpio_irq_chip *girq;
-
-  /* Set up the irqchip dynamically */
-  g->irq.name = "my_gpio_irq";
-  g->irq.irq_ack = my_gpio_ack_irq;
-  g->irq.irq_mask = my_gpio_mask_irq;
-  g->irq.irq_unmask = my_gpio_unmask_irq;
-  g->irq.irq_set_type = my_gpio_set_irq_type;
-
-  /* Get a pointer to the gpio_irq_chip */
-  girq = &g->gc.irq;
-  girq->chip = &g->irq;
-  girq->parent_handler = ftgpio_gpio_irq_handler;
-  girq->num_parents = 1;
-  girq->parents = devm_kcalloc(dev, 1, sizeof(*girq->parents),
-                               GFP_KERNEL);
-  if (!girq->parents)
-      return -ENOMEM;
-  girq->default_type = IRQ_TYPE_NONE;
-  girq->handler = handle_bad_irq;
-  girq->parents[0] = irq;
-
-  When this is done, we will delete the old APIs for instatiating
-  GPIOLIB_IRQCHIP and simplify the code.
-
 - Look over and identify any remaining easily converted drivers and
   dry-code conversions to gpiolib irqchip for maintainers to test
 
-- Drop gpiochip_set_chained_irqchip() when all the chained irqchips
-  have been converted to the above infrastructure.
-
-- Add more infrastructure to make it possible to also pass a threaded
-  irqchip in struct gpio_irq_chip.
-
-- Drop gpiochip_irqchip_add_nested() when all the chained irqchips
-  have been converted to the above infrastructure.
-
 
 Increase integration with pin control
 
@@ -191,3 +142,39 @@ use of the global GPIO numbers. Once the above is complete, it may
 make sense to simply join the subsystems into one and make pin
 multiplexing, pin configuration, GPIO, etc selectable options in one
 and the same pin control and GPIO subsystem.
+
+
+Debugfs in place of sysfs
+
+The old sysfs code that enables simple uses of GPIOs from the
+command line is still popular despite the existance of the proper
+character device. The reason is that it is simple to use on
+root filesystems where you only have a minimal set of tools such
+as "cat", "echo" etc.
+
+The old sysfs still need to be strongly deprecated and removed
+as it relies on the global GPIO numberspace that assume a strict
+order of global GPIO numbers that do not change between boots
+and is independent of probe order.
+
+To solve this and provide an ABI that people can use for hacks
+and development, implement a debugfs interface to manipulate
+GPIO lines that can do everything that sysfs can do today: one
+directory per gpiochip and one file entry per line:
+
+/sys/kernel/debug/gpiochip/gpiochip0
+/sys/kernel/debug/gpiochip/gpiochip0/gpio0
+/sys/kernel/debug/gpiochip/gpiochip0/gpio1
+/sys/kernel/debug/gpiochip/gpiochip0/gpio2
+/sys/kernel/debug/gpiochip/gpiochip0/gpio3
+...
+/sys/kernel/debug/gpiochip/gpiochip1
+/sys/kernel/debug/gpiochip/gpiochip1/gpio0
+/sys/kernel/debug/gpiochip/gpiochip1/gpio1
+...
+
+The exact files and design of the debugfs interface can be
+discussed but the idea is to provide a low-level access point
+for debugging and hacking and to expose all lines without the
+need of any exporting. Also provide ample ammunition to shoot
+oneself in the foot, because this is debugfs after all.