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[0/4] gpiolib: cdev: relocate debounce_period_us

Message ID 20231212054253.50094-1-warthog618@gmail.com
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Series gpiolib: cdev: relocate debounce_period_us | expand

Message

Kent Gibson Dec. 12, 2023, 5:42 a.m. UTC 
This series contains minor improvements to gpiolib-cdev.

The banner change is relocating the debounce_period_us from gpiolib's
struct gpio_desc to cdev's struct line.  The first patch stores the
field locally in cdev.  The second removes the now unused field from
gpiolib.

The third patch is somewhat related and removes a FIXME from
gpio_desc_to_lineinfo().  The FIXME relates to a race condition in
the calculation of the used  flag, but I would assert that from
the userspace perspective the read operation itself is inherently racy.
The line being reported as unused in the info provides no guarantee -
it just an indicator that requesting the line is likely to succeed -
assuming the line is not otherwise requested in the meantime.
Give the overall operation is racy, trying to stamp out an unlikely
race within the operation is pointless. Accept it as a possibility
that has negligible side-effects and reduce the number of locks held
simultaneously and the duration that the gpio_lock is held.

The fourth patch is unrelated to debounce or info, but addresses Andy's
recent assertion that the linereq get/set values functions are confusing
and under documented.  Figured I may as well add that while I was in
there.

Kent Gibson (4):
  gpiolib: cdev: relocate debounce_period_us from struct gpio_desc
  gpiolib: remove debounce_period_us from struct gpio_desc
  gpiolib: cdev: reduce locking in gpio_desc_to_lineinfo()
  gpiolib: cdev: improve documentation of get/set values

 drivers/gpio/gpiolib-cdev.c | 257 ++++++++++++++++++++++++++++--------
 drivers/gpio/gpiolib.c      |   3 -
 drivers/gpio/gpiolib.h      |   5 -
 3 files changed, 201 insertions(+), 64 deletions(-)

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2.39.2