[PATCH v3 0/2] pinctrl: pinmux: Add pinmux-select debugfs file

[Drew Fustini <drew@xxxxxxxxxxxxxxx>]

This series first converts the debugfs files in the pinctrl subsystem to
octal permissions and then adds a new debug file "pinmux-select".  Add
function name and group name can be written to "pinmux-select" which
will cause the function and group to be activated on the pin controller.

Notes for PATCH v3:
- add Suggested-by: Andy Shevchenko to the "pinctrl: use to octal                                     
  permissions for debugfs files" patch
- change the octal permissions from 0400 to 0444 to correctly match the                         
  symbolic permissions (thanks to Joe Perches and Geert Uytterhoeven)    
- note that S_IFREG flag is added to the mode in __debugfs_create_file()
  (thanks to Andy for highlighting this and Joe for suggesting I should 
  add a note to the commit message)
- fix order of the goto labels so that the buffers are freed correctly
  as suggested by Dan Carpenter 
- move from devm_kzalloc() to kzalloc() as the buffers are only used
  inside the pinmux_select() function and not related to the lifetime
  of the pin controller device (thanks to Andy for pointing this out)
- correct the pinmux-select example in commit message to use the
  function and group name instead of selector (thanks to Geert)

Notes for PATCH v2:
- create patch series that includes patch to switch all the debugfs
  files in pinctrl subsystem over to octal permission
- write function name and group name, instead of error-prone selector
  numbers, to the 'pinmux-select' file
- switch from static to dynamic allocation for the kernel buffer filled
  by strncpy_from_user()
- look up function selector from function name using
  pinmux_func_name_to_selector()
- validate group name with get_function_groups() and match_string()
- look up selector for group name with pinctrl_get_group_selector()

Notes for PATCH v1:
- posted seperate patch to switch all the debugfs files in pinctrl
  subsystem over to octal permission [1]
- there is no existing documentation for any of the debugfs enteries for
  pinctrl, so it seemed to have a bigger scope than just this patch. I
  also noticed that rst documentation is confusingly named "pinctl" (no
  'r') and started thread about that [2]. Linus suggested chaning that
  to 'pin-control'. Thus I am planning a seperate documentation patch
  series where the file is renamed, references changed and a section on
  the pinctrl debugfs files is added.

Notes for RFC v2 [3]:
- rename debugfs file "pinmux-set" to "pinmux-select"
- renmae pinmux_set_write() to pinmux_select()
- switch from memdup_user_nul() to strncpy_from_user()
- switch from pr_warn() to dev_err()

[1] https://lore.kernel.org/linux-gpio/20210126044742.87602-1-drew@xxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-gpio/20210126050817.GA187797@x1/
[3] https://lore.kernel.org/linux-gpio/20210123064909.466225-1-drew@xxxxxxxxxxxxxxx/

Drew Fustini (2):
  pinctrl: use to octal permissions for debugfs files
  pinctrl: pinmux: Add pinmux-select debugfs file

 drivers/pinctrl/core.c    |   6 +--
 drivers/pinctrl/pinconf.c |   4 +-
 drivers/pinctrl/pinmux.c  | 111 +++++++++++++++++++++++++++++++++++++-
 3 files changed, 114 insertions(+), 7 deletions(-)

-- 
2.25.1