Messages in this thread | | | Date | Sat, 6 Aug 2022 10:53:16 +0200 | From | Christophe JAILLET <> | Subject | Question: dev_err_probe() vs Printk Index |
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Hi,
When a driver is using dev_err(), part of it is inlined and it: - takes advantage of dev_fmt() [1] - implements Printk Index [2]
Printk Index works with some __builtin_constant_p() magic in it. In case of a use in a probe, 99.99% of the time the log level and the format will be constant and the logic for Printk Index will be put in place.
In case dev_err_probe(), the format will be an argument passed to the function and will not be constant, so nothing will be generated in the 'printk'_index section.
In case dev_err_probe(), a potential dev_fmt() defined in the drivers' file can't be taken into consideration. (trusting my grep, we never use in files that define dev_fmt() in the .c file. I've not checked if it is true via #include "<something.h>")
Even if I've read [3], I don't fully understand the real need of this Printk Index mechanism (at least for my own needs :))
My questions are: - is my analysis right? - is the lack of these 2 functionalities (dev_fmt and Printk Index) expected, when dev_err_probe() is used? - if not, is it a issue? - should it be at least documented?
(not sure who to put in copy of this mail)
CJ
[1]: https://elixir.bootlin.com/linux/v5.19/source/include/linux/dev_printk.h#L143 [2]: https://elixir.bootlin.com/linux/v5.19/source/include/linux/dev_printk.h#L107 [3]: Documentation/core-api/printk-index.rst
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