gpio: Add GPIO Aggregator
GPIO controllers are exported to userspace using /dev/gpiochip*
character devices. Access control to these devices is provided by
standard UNIX file system permissions, on an all-or-nothing basis:
either a GPIO controller is accessible for a user, or it is not.
Currently no mechanism exists to control access to individual GPIOs.
Hence add a GPIO driver to aggregate existing GPIOs, and expose them as
a new gpiochip.
This supports the following use cases:
- Aggregating GPIOs using Sysfs
This is useful for implementing access control, and assigning a set
of GPIOs to a specific user or virtual machine.
- Generic GPIO Driver
This is useful for industrial control, where it can provide
userspace access to a simple GPIO-operated device described in DT,
cfr. e.g. spidev for SPI-operated devices.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
---
v6:
- Use gpiod_to_chip() instead of open-coding,
- Drop debug print of gpio_desc.label, as it usually just points to
the GPIO Aggregator itself,
- Drop no longer needed #include "gpiolib.h",
- Fix missing offset translation in gpio_fwd_set_config(),
- Use GPIO_LOOKUP_IDX() to populate struct gpiod_lookup,
v5:
- Add Reviewed-by, Tested-by,
v4:
- Remove unused assignment to n in isrange(),
- Check correct pointer after aggr->lookups->dev_id allocation,
- Preinitialize flags to 0 in gpio_fwd_[gs]et_multiple() to avoid
may-be-used-uninitialized warning,
- Drop controversial GPIO repeater,
- Update for gpiod_lookup.chip_label rename,
- Use %pe to format error pointers,
- Use U16_MAX instead of (u16)-1,
- Correct comment indentation,
- Use skip_spaces() helper,
- Rename a and b to first_index resp. last_index,
- Add comment to tmp[] use,
- Improve Kconfig help text,
- Include <linux/gpio/consumer.h> for gpiod_[gs]et_*(),
- Drop unneeded valid_mask handling,
- Add comment about sleeping and .set_config() support,
v3:
- Absorb GPIO forwarder,
- Integrate GPIO Repeater and Generic GPIO driver functionality,
- Use the aggregator parameters to create a GPIO lookup table instead
of an array of GPIO descriptors, which allows to simplify the code:
1. This removes the need for calling gpio_name_to_desc(),
gpiochip_find(), gpiochip_get_desc(), and gpiod_request(),
2. This allows the platform device to always use
devm_gpiod_get_index(), regardless of the origin of the GPIOs,
- Move parameter parsing from platform device probe to sysfs attribute
store, removing the need for platform data passing,
- Use more devm_*() functions to simplify cleanup,
- Add pr_fmt(),
- General refactoring,
v2:
- Add missing initialization of i in gpio_virt_agg_probe(),
- Update for removed .need_valid_mask field and changed
.init_valid_mask() signature,
- Drop "virtual", rename to gpio-aggregator,
- Drop bogus FIXME related to gpiod_set_transitory() expectations,
- Use new GPIO Forwarder Helper,
- Lift limit on the maximum number of GPIOs,
- Improve parsing:
- add support for specifying GPIOs by line name,
- add support for specifying GPIO chips by ID,
- add support for GPIO offset ranges,
- names and offset specifiers must be separated by whitespace,
- GPIO offsets must separated by spaces,
- Use str_has_prefix() and kstrtouint().
3 files changed
