[PATCH v5 0/2] pinctrl: pinmux: Add pinmux-select debugfs file

From: Drew Fustini
Date: Fri Feb 12 2021 - 17:44:10 EST


This series first converts the debugfs files in the pinctrl subsystem to
octal permissions and then adds a new debugfs file "pinmux-select".

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 v5:
- convert permissions from symbolic to octal for debugfs_create_file()
calls in core.c that Joe Perches pointed out I had missed
- Linus W: please let me know if I should break this series apart as you
already applied an earlier version of octal conversion patch today [1]
- switch from sscanf() to just pointing to function name and group name
inside of the buffer. This also avoids having to allocate additional
buffers for fname and gname. Geert and Andy highlighted this security
issue and Andy suggested code to use instead of sscanf().
- switch from devm_kfree() to kfree() after Dan Carpenter warned me
- remove .read from pinmux_select_ops per Geert since it is write only
- add usage format to error when unable find fname or gname in buffer

Notes for PATCH v4:
- correct the commit message in the second patch to reference function
and group name instead of integer selectors. Apologies for not fixing
that in v3
- fix typos in cover letter

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
- 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 | 12 ++---
drivers/pinctrl/pinconf.c | 4 +-
drivers/pinctrl/pinmux.c | 103 +++++++++++++++++++++++++++++++++++++-
3 files changed, 109 insertions(+), 10 deletions(-)

--
2.25.1